Difficult to say, in fact, and in some way I like all kind of classes.
But honestly? Most of all I like magical spells, so a Mage is what I take mostly, but never a pure mage because I like to change now and then (variation!) a bit, so that's the reason I play now not as a Mage, but as a Ranger Mage. In Divinity II (DKs) I play now as a Ranger Priest.
The very first playthroughs that I started to play RPG's I mostly take a Sword (and Shield).
After a long time I try other things out and DD is a perfect rpg to try out many things ! Even use a Spear now, something I never did before ! And a Bow ! But use mostly Elemental Arrows with the bow, great & strong skill !
O, DD is really, really wonderful !!
Can't say it enough, sorry I say it agian and again, but .. can't say it enough ... Divine
is a Masterpiece and it can't get out of my Mind, never,
it's forever !!