Hang on a sec guys, General is probably better for Gilliam because he only loses one point of move and everything else is better (pretty much). The reason Amelia wants to go Great Knight is so that she can go Cavalier first, because otherwise there is little realistic chance of training her.
But yeah, the difference between Great Knight and General actually kind of favors General, and since Gilliam is forced into being a Knight anyway, he may as well become a General.
Basically, it's a trade between 2 Con, 2 Res, 1 Skill, 1 Speed, and 1 HP against 1 point of Move. Plus General has better caps, but caps aren't mega likely to actually matter, etc, etc.
Oh yeah, and you don't fear Horseslayers, for all that's worth.