My 2 coppers...
I find that sorcerers make an excellent one-level multiclass option if you feel like your rogue or fighter could use a little magical "oomph" from time to time or to qualify for a nifty prestige class, sorcerer is the way to go.
If you're looking to pick up just enough magical "power" to enchant items, though, I have to favor wizards. Multiclass three levels and get access to the Craft Wondrous Item Feat - with 2nd level spells to choose from in creating stuff. Multiclass for five levels and you get fireball, lightning bolt, and a bonus feat (which, if you're smart, you probably use for Craft Wand).
If you want to play a counterspeller, you gotta love the sorcerer - (especially with the Heightened Spell Feat if you rule that a sorcerer can't use a 4th level slot on a 3rd level spell) - while no wizard is going to memorize a ton of dispel magic spells, the counterspelling sorcerer can burn a ton of slots on dispels.

And in my experience, a counterspeller is particularly potent at high levels of play.
But properly played, a wizard is every bit as dangerous as a sorcerer - do not overlook those bonus Feats! After his first adventure, any self-respecting Wizard ought to be going straight home and burning as much gold and/or XP as he can to Scribe Scrolls. Any fifth level wizard worth his salt immediately uses his Bonus Feat to pick up Craft Wand and proceeds to craft a wand or five of Fireball, a wand or five of Lightning Bolt, and then memorizes his "non-combat" spells when adventuring. Wizards should be using their bonus feats on item creation feats (IMO) and use the items to give them the "on-demand" combat ability. And any Wizard who isn't Crafting Staffs as soon as he hits 12th level is just stupid. Staffs (and to a lesser degree, Wands) are referred to by my wizard characters as "sorcerer-on-a-stick."
Value of a "sorcerer-on-a-stick" (Staff) with the same number and level of spells "known" as a 12th-level sorcerer (and with a caster level of 12) - 153,000 gp. (If all spells draw two charges, it drops to 76,500 gp). Remember, though, that it costs only half that much gold to "do it yourself" with the Craft Staff Feat.
Value of a "sorcerer-on-a-stick" (Staff) with the same number and level of spells "known" as a 10th-level sorcerer (and with a caster level of 10, the damage cap for fireballs and lightning bolts) - 87,187 gp. (If all spells draw two charges, it drops to 43,593.5 gp). Remember, though, that it costs only half that much gold to "do it yourself" with the Craft Staff Feat.
The 10th-level sorcerer-on-a-stick costs a wizard 3487.5 XP and the 12th-level SoaS costs a wizard 6,120 XP. (Halved if the wizard creates a SoaS that has all effects draw two charges). Yes, these are significant outlays... the 6,120 XP, for instance is about half of what the wizard needs to advance to 13th level. But IMO, it's a sacrifice that is definitely worth it - you now have all the strategic flexibility of being a wizard with the tactical flexibility of being a sorcerer - and now you know why fantasy wizards are always carrying staffs!
Does this make wizards a little more reliant upon their "stuff?" Absolutely. But that's a factor in every class nowadays, so it's not that bad.
--The Sigil