Sorcerers largest advantage, in my opinion, lies not in their number of spells per day or even the "I can cast from whatever I know" aspect of spontaneous casting.
Rather, I think their largest advantage is that they have no need to prepare spells. The importance of this advantage varies by the campaign in which you play. If your DM has you attacked in the middle of the night frequently, or has you kidnapped frequently, or has your possessions stolen frequently, the life of a sorcerer is much more attractive than that of a wizard. With the eschew materials feat from TaB (or the alternate sorcerer), you can cast any spell from your repetoire stark naked after being beaten all night.
The sorcerers disadvantage really lies in spell selection----one can look at the "spells known" table for a level 20th sorcerer and it doesn't look all that bad. However, remember that you have to progress through all those levels and the decisions become much harder when you can only know one spell per level. Stock up on combat spells? Sure...but you will be nigh-on worthless in non-combat oriented adventures.
The wizard's advantage really does lie in spell selection but the need to be well rested and have a spell book to prepare spells is a huge weakness. This, again, varies by campaign. If you never get your spell book stolen (or damaged), or get kidnapped, or being attacked in the dead of night is rare, the wizard is much more attractive than the sorcerer. However, even one adventure (or one night of gaming) in which you find yourself totally unable to cast spells can be unpleasant to say the least.
Spell mastery mitigates this to some extent, at least giving you the opportunity to prepare spells when your spell book is gone. However, you *still* need to be rested so you can easily find yourself totally unable to prepare spells if a campaign is particularly hectic.
On the plus side, the wizard can really rock and roll, particularly if the campaign allows you the time to rest, to prepare spells, and most importantly, time and money to prepare magical items such as scrolls and wands. With the free scribe scroll feat, a wizard can prepare combat spells that will make him almost as effective (and depending on level of spells available, sometimes more effective) artillery than a sorcerer, while at the same time carrying scrolls of spells that he won't use every day but it is very handy to have when you need. You may carry that scroll of comprehend languages or detect secret doors around for three levels before you use it, but when you need it *poof* you have it at the cost of a few experience. Similarly, wands of frequently used spells can be handy, particularly to boost your combat capability (as, unlike scrolls, they do not evoke at attack of opportunity).
A wizard well prepared with scrolls and wands can be devestating and versatile. Additionally, if a party is careful about gathering information and goes into adventures well informed, the wizard can make strong spell selections that make her truly shine. However, if in a party ( like most of mine are) that function in a constant state of surprise and chaos, the sorcerer is probably a better choice.