Although Marcus does seem to have better stats (and apparent popularity), I think Isadora still has a chance to be a good unit. I have not gotten her to Lv. 20 before, but she has about the same HP and Str as Marcus, statistically speaking. Her strength is just as good as Marcus', but she has a lower base. Her avoid can be +25 over Marcus', and she has a better chance at dodging criticals. Although that may not be enough to convince anyone to change their opinion of her, I still think she could be as great as Marcus could be. :D