Well, it depends (of course). At 30, that Sorceror could very well have Master Staff. If the DM permits hiring out magic item creation for custom items, that Sorceror could effectively have every spell on his list, a few of them at a time (although, in theory (read: if he has the cash, and the DM allows it), he could hire a few dozen high-level wizards to enchant a staff with EVERY spell on the default Sor/Wiz list at 2 charges apiece and have them all at once). Of course, nothing stops the Wizard from doing this as well to swap out prepared spells for others.
Likewise, it depends on how the fight starts - two random spellcasters meeting in an open field and simultaneously deciding they are going to kill the other? The Sorceror's flexibility will likely win the day (Need all the 9th slots to be your offensive spell today? No Problem, for a Sorceror). Two spellcasters that know each other well meeting for a duel in three days time? The Wizard's tactical planning ability will likely carry the day. With a surprise attack (Scry, Buff, Teleport) whoever attacks is most likely to win.
Likewise, at 30, that Sorceror could have Epic spells (as could the wizard) that do nasty things, and in a battle of purely epic spells, neither really has an advantage over the other (other than the Wiz's greater feat rate).
Also at 30, that Sorceror could have prestige classes that boost flexibility - Archmage comes to mind, and Elemental Mastery, but I'm sure there are many other good candidates - to multiply the effective spell list of the sorceror. The Wiz can also do this, but benefits less from altered spells as the Wiz's spell list will be more varied anyway.
It depends. A lot. As Aust Diamondew said, the bigger munchkin has better odds.