Personally - I have an affinity for Sorcerers, but I don't like the RDD prestige class myself. (Although others do).
The main difference between the two classes is how their spell casting works. This is descriped in the manual, so I will not go to deep into it here.
Just know that a wizard knows more spells and a sorcerer can cast fewer known spells more often.
Basically - I'd say that the wizard is likely more powerfull *if* he has prepared proberly.
The Sorcerer is more allrounded spellcaster, because he dosen't have to memorize spells, but again - he also knows fewer spells.
Besides the mechanics of spell casting, there are a few other more subtle differences.
Skills....
A wizard will gain many more skillpoints then a sorcerer, because a wizards main attribute is intelligence, and this governs skillpoints. This means more points to put into concentration, lore, spellcraft and others as you wish (Tumble
).
Also a wizard gains access to bonus feats usable for meta-magic.
But personally - I still think the Sorcerer is the more versatile spellcaster, but overall the Wizard proberly has most things going for him. This is of couse always somewhat subjective, but bonus-wise a wizard gains more.
But I've never been able to adapt to a wizard in NwN for some reason.
I've not tried out the Palemaster prestigeclass, so I can't comment on that one. But from now on - I'll stay away from the RDD unless playing a bard or using it as a multiclass for a fighter-type.
But, in conclusion - it all comes down to how you like to play. My advice is to try both of them out for a while, and then decide wich one to commit to.