*warning: what follows is an example of what is called "min/maxing" or "munchkinism"*
I tend to use sorcerors if I want my multiclass character to have some low level magical ability or if the dm is really picky about spellbooks, carrying capacity and page counts (books are heavy, wizards are not usually all that strong). you know, invisibility, and magic detection for my rogue, bulls strength for my warrior guy, that sort of thing. if i just want the magical power, i go wizard because you get the spells faster and your casting attribute also gives you more skill points for things like concentration and spellcraft. Also, take the mind over body feat for the love of god. also, i find that whatever spells i pick with a sorceror, they will not be the ones i need, i like versatility and situational customizability. I am the sort of guy who has five different spell lists prepared for my wizard depending on the area he is in and the expectations he has for the day (urban, forrest, mountain, underground, and generic guaranteed heavy combat)