I will pitch in with the campaign-depended crowd. Heck, it's even encounter-specific.
If you have 10 encounters a day, then, yeah, the Sorcerer will shine. If you have 2, but big ones, chances are the Wizard will shine.
In our group, believe it or not, the characters that seem the weakest are the pure Cleric and a Wizard/Cleric. I play a Wizard and another plays the Sorcerer (going for DD). And there's a Rogue, a Fighter and a Monk. We are at 15th level.
The Fighter is a total tank. He dishes out damage like there's no tomorrow. Against a single big baddie, the Wizard doesn't even bother casting. He knows the baddie is toast within 3 rounds if the Fighter can close and use his full attack (intelligent Greatsword). The Sorcerer may assist the Fighter, or not.
The Rogue is good, but in limited circumstances. She's an archer, and has to be close to use her sneak attack. If she gets it, goodbye baddie. She's the unlocker and trap disarmer as well.
The Wizard is the WMD guy. Lots of targets, he casts. Nothing will clear the field like an Empowered Firebrand. He buffs the Monk and Fighter with protective spells early in the day using Extend Spell, which last all day. Hes the party know-it-all and frequently uses his Knowledge and Spellcraft skills. Identifies monsters, items and spell effects. And he scribes scrolls for the Sorcerer.
The Sorcerer basically participates all the time, but in a measured fashion. He basically chips away at the opposition constantly, compared to the Wizard's infrequent Big Bang.
The Monk is not as totally smackdown as the fighter, but he's damn impressive. SR, Flurry, Trips, all we see is a cloud of hands and feet, and then a dead baddie.
The Cleric basically fixes us up after a nasty fight, resurrects, buffs, etc. The Cleric/Wizard's role varies, but he's definitely a support type.
Bottom line is, the Wizard shines with his large selection of buffing spells that last all day and WMD spells that can wipe out a whole battlefield. The scrolls also give the Sorcerer some versatility. The Sorcerer is good at dishing out constant amounts of damage, one time, all the time.
All in all, I think the Wizard and Sorcerer synergy is great. The Wizard can choose his spells less carefully as he knows that the Sorcerer will be there for just about any situation. And the Sorcerer can use scrolls in a tight spot when he needs a spell he doesn't know.
Andargor