I prefer something in the middle, I don't like having to manage everything including base stats and such (not to mention that makes the characters so homogeneous), but no customization at all goes too far.

A system I really like is the Quartz system in Legend of Heroes: Trails games:
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This one in particular is a slightly older version of the system they use in Trails of Cold Steel, basically you have a master quartz that gives a big stat boost or special effect, then smaller quartz that on top of giving smaller boosts/effects, also give you points in certain elements (see the two lines near the bottom). How many points you have on any one line decides which spells that character can cast, so for example having 4 water points gives you some heals and minor water spells, having 12 water points gives you a massive water spell. But only if they're on the same line, so if you have 6 water on one line and 6 water on the other line, you don't get the big 12 point spell.

It's nice and simple, and with the right setup you can still alter a character's power/role in battle fairly drastically. It's also like a puzzle to figure out how you're going to spread your quartz across your party.

Sadly in Cold Steel they got rid of the points thing and quartz just give spells individually.