Individual skills, or skill categories? Options

[Eiyu]

Just curious. In a game that offers customisation in learning and mastering skills - which do you prefer?

An example of categories; Black Magic contains every offensive magic spell. A character's potency with offensive spells is based on his/her black magic skill level, and s/he'd end up learning every spell in the category.

An example of individual skills; the more you use Fire or allocate points into it, etc, the better at casting Fire you'll get. Learning Fire doesn't mean you'll ever learn Water, nor will it increase your potency at casting Water.

Trying to figure out what the best course of action would be for my customisation. At the moment I seem to be going with categories but I'd like more feedback. Many thanks.

[PianoOnWheels]

I personally prefer the first of the two.

The second one seems like a good idea, but the problem seems to be if, say, you're up against a boss that is weak to water but you've been leveling up nothing but your fire spells. Seems like it would be kind of annoying.

PoW

[Eiyu]

That makes sense, yeah. I have 3 characters and want to give them a choice of 6 classes (for now). Just wanna make sure it's not too restrictive.