Dr. Awkward said:So, you plan not to answer the question, then? I asked why you say they're flexible. You said "they're flexible." That doesn't give any reasons supporting your assertion. Can you please back this up with something material? You say they're flexible because they're adaptable. Why are they more adaptable?
Because of metamagic.
If you design your Sorcerer well, he not only has the 3rd level spell slot Fireball, but he also has the 5th level spell slot Empowered Fireball and the 3rd level spell slot Energy Substitution Coldball and the 5th level spell slot Energy Substitution Empowered Coldball.
Throw some Metamagic Rods into the mix and a Sorcerer can become truly devastating whereas the Wizard just becomes powerful.
Protection From Energy. The Wizard might have one or two. The Sorcerer can stop multiple different energy types in a single combat, plus he can stop energy damage on multiple allies.
The real aspect of adaptability, though, is the fact that the Sorcerer is almost always prepared for any situation he can handle whereas the Wizard may or may not be. The Wizard might, given time, be able to handle more different types of situations, but he cannot repeatedly handle the same subset of situations over and over again that the Sorcerer can unless he has some foreknowledge that the given situation will occur over and over again.