The biggest downside to wizard is that there is very little reason to go several levels in Wizard. You only need 1 lvl to get access to every wizard spell in the game.
Specialisation bonuses
What you quoted said 'very little reason' - not no reason. But I would agree that in some cases the level 2 spec bonus is pretty juicy, so you would likely want to go 2 levels in.
But still, with some specialization in a particular element a Sorcerer 10/Wizard 2 is superior to the Wizard in pretty much every way and can learn all spells. You can get sculpt spells, learn all spells, have stat bonus to one element of your choice and metamagic.
