If it is a single-player RPG, I want to play a character that can cast at least some magic because quite often the magic part is much more interesting and diverse with lots of spells, than just trying to decide whether to use a sword or axe, or try to find the strongest plate mail. And then you have to buy lots of healing potions and maybe some rechargeable magical items, while a spellcaster gets all those for free, and doesn't have to buy or recharge anything, after acquiring the spells.
On the other hand, I don't want to depend only on magic either, the character should always have means to fight even if he can't cast spells for some reason (be it lack of spellpoints and no means to rest, or someone has casted a Mute/Silence on me, or somesuch).
For instance, in TES Arena, a plain mage is fine because he can still fight quite well with a staff (Staff of Magnus), as long as you puff up the fighting skills. At the same time, you have access to all those useful spells, and you don't need to keep buying/recharging them in shops.
On TES: Daggerfall, I selected a Spellsword instead (which is like a lesser mage with some melee fighting abilities, I guess), just in case. I wasn't sure if a mere mage could have fought similarly as in Arena, some FAQs implied that a pure mage in Daggerfall should always avoid melee fight, which was not what I wanted either especially as casting combat spells in Arena/Daggerfall is quite cumbersome.
All in all, I prefer party-based RPGs because there I don't have to make the choice. I can have both kickass warriors, mages, healers and thieves, or even something esoteric like bards, all in the same party. Ah, Icewind Dale....
Post edited December 21, 2015 by timppu