Bors is bor ing. And he sucks. He's a knight, and he has all the phailures associated with them, but without the benefits. He has low move, and he's slow so he gets doubled, etc., but he's not tanky and doesn't have high atk.
In the first chapter, he's getting doubled by half the enemies, and he dies in 3 hits. And he's melee, so he eats a counterattack when he attacks. And he has about 56 hit on them, so he misses half the time. So trying to do anything with him is usually counterproductive.
Chapter 2 is a bit better since it has soldiers in addition to fighters. His low move hurts him more, though, since after the first group of enemies, you have to hurry to the other side of the map, where Deak's group is already fighting and pushing back the enemy line, so he doesn't see much, if any action, after the first enemy group.
In chapter 3, he finally doesn't fail completely. There are only two fighters, and he's pretty decent against all the soldiers, though his hit is still only about 75 on them. And he's still hindered by his low move. After the first couple of turns, enemy density is pretty low until you get closer to the throne and run into those cavalier reinforcements, so he falls behind then. Either that or you send him to go help recruit Lugh or get that Mend staff, in which case he sees even less combat.
Ch 4, however, is almost as bad as ch 1. There aren't any loldiers for him to fight, and he gets doubled by everything, and his sucky hit is sucky, since these enemies have existant spd and therefore have existant avoid. He has about 59 hit on them. 69 on the few ones with swords. And the fact that he fails so massively in the previous chapters (not reaching enemies, missing, or just not attacking due to doing so being a bad idea (ch1 mostly), etc.) means he didn't get much exp, so his level is pretty low.
Then ch 5 is mostly axes again, and their spd went up more since ch 1 than his did (They have 8-10 spd), so he's fail incarnate. Either they use steel axes, rendering his def worthless, taking off well over half his hp anyway, or they double him, which is worse, since he can potentially get one-rounded. They can have up to 22 atk (23 after WTA) along with their ~9 AS. That one-rounds 12 def and 22 hp, which is pretty averageish for Bors at this point. And since their spd went up, their avoid went up as well. He gets like 52 hit on the ones that don't have steel equipped. And some of them are on forests. Enjoy your AIDS.
Ch 6 has a lack of axes and instead features lots of lances, with more loldiers than anything else. Yaye, Bors can actually gain exp. There are quite a few mages, too, though. Magic hurts on his 0 res, lopping off about half his hp with each hit. They're not fast, fortunately for him, so he doesn't get one-rounded. But that can get him killed, even with only one mage, since loldiers (and knights) have good str if nothing else, and some have steel lances.
Ch 7 fortunately has no axes, but it has few soldiers, which sucks for Bors since his offense is mad fail on anything else. And those wyverns are dangerous for everyone, but especially for Bors since he gets doubled and potentially one-rounded. Then you have a lot of ground to cover to get to the throne, so his low move limits his combat exposure. In addition to the limits imposed by his durability issues.
Then ch 8 is like hell for low move units. It has a super long stretch of low enemy density, so everyone that's not mounted is using all their move almost every turn for quite a while, until you get to that knot of enemies shortly past Barth/OJ/Wendy's joining spot. To give you an idea of just how long that is, it takes Bors 12 turns to get there if he uses his full move every turn. After that little group, you have quite a bit of ground to cover yet again. From there to the throne is almost just as far. Enemy density is near zero for several turns after this. And here is where Lilina joins. In the downtime starting the second half of ch 8, before the flood of enemy reinforcements.
Bors is about level...
Let's see... he gets crap all from ch 1, maybe half a lv from ch 2, a level from ch 3, like half a level from ch 4, crap all from ch 5, two levels from ch 6, a level from ch 7, and little to nothing from the first half of ch 8. That comes out to about 5 levels, which puts him at lv 6, so I'll give him lv 7.
Omg Lilina's stats are even lower than Bors's! But there are several very important differences. First of all, I'll talk about supports. Bors has absolutely no supporters, fail or otherwise, until chapter 8, so I haven't even made mention of supports until now. Bors's supports are pretty terrible. He has Lilina, Barth, and Wendy, who are all low/bottom tier trash. Then there's Astol and OJ, who are mid tierish. Astol is just a theif, and usually a secondary one at that, so he's only getting fielded on chapters with things to steal and such, and sometimes not even then since Chad may be able to handle it by himself. And when he is fielded, he's off doing thiefy things most of the time, and making use of his 6 move vs Bors's 4. So this support is pretty worthless as well. So OJ is all that's left. He's not low tier, but the gap between high/top tier and mid tier is pretty huge in this game, so he's still pretty meh. He may or not get used. So Bors has one iffy support.
Lilina, on the other hand, has a huge 10-unit support list. She basically has Bors's support list plus 5 other units. Bors, Barth, Wendy, and Astol can be safely thrown out for reasons already stated, and OJ is iffy. For the other half of her list... She has an instant C with Roy, and Gonzales is quite pwn and finds his best support in Lilina. Those are her two best supports. Then there's also a support with Marcus, who is pretty lol after earlygame, and Garret and Cecilia, who are useable but aren't good at all. They're a fair bit worse than OJ.
Moving on, the next important difference is that fire has 25 more hit than an iron lance. That's pretty huge. Bors has crappy hit (about 85 before enemy avoid), whereas Lilina's is pretty good (112).
The next difference is that Lilina's attacks have 1-2 range. No eating counterattacks for this little girl, much unlike Bors. This helps tremendously on keeping her alive. It also lets her be removed from the enemy a bit, which does two things: She can attack while still being behind others, further helping with staying alive, and she doesn't get in the way of someone like Deak or Lance attacking the enemy. Bors attacking often actually hurts you offensively since you have him attacking with his crappy hit and meh power and zero AS instead of someone with much better offense, whereas Lilina's damage is pretty much always in addition to someone else's, so she's actually helping.
Next, Lilina's attacks hit res, which is generally much lower than def. Bors currently has 5 more atk, but they do silimar damage because of this point. Lilina also has a 75% mag growth and is lv 1, so her damage is going up very quickly. Bors has a pretty low 30% str growth, and he's currently gaining 18 less exp per kill due to being 6 levels higher.
And the last difference is the coming chapters. After ch 8, enemy composition becomes heavily axe-based, which spells very bad news for Bors. It's like ch 5 all over again, but for 5 full chapters, and somewhat in 8x, too. Have fun missing half the time. Have fun getting counterattacked for half your hp and then being stuck there, in enemy range, and making it harder for someone else to follow up. Aside from using Wendy, using Bors is the worst thing you can be doing in these chapters.
Oh, one more thing: Bors's move sucks. And not only does Lilina have more move, but her effective attack range is larger due to ranged weaponry. Bors can reach 5 tiles from where he stands, aside from pulling out a loljavelin, which has 15 less hit than his already fail hit. Lilina's range is 7.
With all that missing (missing gives 1 exp), falling behind, and just fail in general that Bors is doing in addition to him being on a higher level, he's gaining much less exp, so Lilina catches up in level pretty quickly. If Bors miraculously manages to gain a level in every one of those chapters, he's about lv 14 by the end of it.
Well, let's take a look at their performance midway through it.
Ch 11's fighters average about 28 atk with their steel axes. A lv 11 Bors averages 14.5 def and 29 hp. And 7 spd. So he's right on the border of getting killed in two hits. They average about 11 spd, ranging from 10 to 12, so he also may or may not get doubled by the ones that don't use steel axes. Anyway, his defense is terrible. And as bad as that is, his offense is worse. Bors with an iron lance has 17 atk and about 88 hit. The fighters have 5-6 def, 2-3 res, and like 39 hp, and 15-28 avo (I'll take 20). So he does 10-11 damage with about 58 hit. Oh, and his move sucks.
Lilina at lv 9 gets OHK'd by all of them, but she also doesn't get counterattacked and is much easier to keep from getting attacked, as stated, so if anything, she's easier to keep alive than Bors is. For offense, Lilina with fire also averages 17 atk but has about 117 hit (and hits res). So she does 13-14 damage at ~97 hit. Lilina is clearly much better on offense.
Then Bors gets relief after that hellish series of axe chapters... for one chapter. After ch 13, it's the desert. He has 1 move there. And the most common enemies are axers. Lilina, on the other had has 5 move.
Then 14x-16 have a pretty nice mix of units. Axes, lances, swords, bows, and mages are all there. And then they promote. Now Bors's def is actually high enough for him to be pretty tanky, as long as magic (or armorslaying weapons) isn't involved. And Lilina has enough hp/def to take a hit from even the strongest attacks. Even two hits from weaker things (things that tink Bors) since she's getting +3 def from her Gonzales support, giving her a total of about 8 def at 20/1. Or several hits vs magic, since her res is pretty high (~19) (and Bors takes loads of damage from them since he has about 5 res).
Anyway, now Bors's raw defense is pretty nice, after that +4 def promotion gain and a few levels. But the real issue is what is he doing with this def? He can't very well get into position to be counterattacking much since his move is bad, and there are much better tanks that have 60% more move. And you don't really want him counterattacking things over someone else anyway because his offense is still pretty bad. 20/2-3 Bors with a killer lance has about 26 atk, 106 hit, 14 AS, 36 crit. Just to get an idea of how low that is, compare that to someone who doesn't fail at life (note this is a mid tier unit, not a high/top tier one): Geese with a killer axe on the same level = 31 atk, 114 hit, 14-15 AS, 79 crit. Or kick it up to someone actually good: Alan at this point with a killer lance = 34 atk, 128 hit, 18 AS, 54 crit. So as you can see, Bors's offense is still terrible. Anyway...
20/2-3 Bors with a killer lance has about 26 atk, 106 hit, 14 AS, 36 crit.
20/2-3 Lilina (supported) with aircalibur has about 33 atk, 128 hit, 14 AS, 26 crit, hits res, 51 atk on fliers.
So Lilina wins offense by even more than she did before. She does like 13 more damage per hit (assumed a 6 def/res gap), or 30+ more on fliers, and she has 22 more hit. 10 less crit, though she can trade 2 atk and 5 hit for 5 crit if you really want crit. So she does almost twice as much damage per hit (far more on fliers) and misses much less, so she has over twice as much offense. That's a pretty massive difference.
Then Lilina's offense grows much faster than Bors's. 45 higher atk growth. And she also gains exp faster because...
Then Lilina now also has staves, which seals the deal, if it wasn't already clear before. Massive mag makes her good even with the base Heal, and she gets another exp pool to draw from.
Then it continues about like that for the rest of the game, with the only real difference being that Lilina's damage lead increases.
On ranks, Bors's terrible offense is horrible for the combat rank. Low move and fail in general is bad for tactics, and Lilina is better for exp due to starting out underleveled and getting staves after promotion.