Since you're playing with a paladin, your best chouces are Dynaheir, Quayle and Xan. Unfortunately Dynaheir'll want you to include Minsc as well, or she'll leave after a time. Quayle is unplayable because of his voice (really, he makes Jaheira sound like.. well, like something that isn't annoying at all), he is only a half-mage, and you'll have to wait until very late in the game before you can include him.
Which leaves Xan. Xan cannot learn web, or fireball, or lightning bolt, or... but he can cast them from scrolls and wands. Aside from that "slight" disadvantage, he's a great character as Xan comes equipped with a very useful enchanted dagger with glow-in-the-dark blade, and a wonderful attitude which is sure to influence morale
No competition really, eh?