I think that it's more like two types of Est.
The magic ones usually have really high growths in one stat (usually MAG), average/good growths in others, and are terrible with def/hp, like sophia, nino, ewan, etc. Usually becomes pretty powerful, but can also sometimes turn out pretty average or bad.
However, there are the ones which are weird, like zeiss, which has pretty awesome growths all around and don't really fit the "est" archetype to me.
I dunno really, but i tend to like leveling up est-like characters, cause sometimes i get really good RNG and end up capping magic at level 10 before promotion.