Knights, definitely. They seem fine when they're first unlocked, being the first unit that can equip gobs of heavy armor and whatnot, but their flaws become more apparent as chapters go one: (1) lame speed growth, and can't equip SPD-boosting Thief Hats later on (2) poor base move & jump (3) attack skills have no range. Knightswords help redeem them a little, but they're generally out of the picture for me by chapter 2/3.