Being a specialist is practically a no brainer. An extra spell of that school can be cast at each spell level?! Extremely handy for those higher level spells that you don't get bonus spells to suppliment. This also brings the wizard up from a base 4 spells/spell level/day to a max base of 5 and close to the number of spells a sorcerer can cast/day at base 6, egads! A wizard that has access to as many spells as they want, can fill open spell slots with spells they need at will, and can nearly cast as many spells/day as a sorcerer? Yea what a rip-off.
Besides as a Wizard you always have to choose your repetoire of spells anyhow, limiting you to at least about half (usually considerably less due to costs) of the spells on the spell list. You lose nothing by picking a specific selection of spells and ignoring the rest, since that's what you have to do anyhow more or less, so you might as well specialize and pick the schools wth spells you don't plan on dipping into anyhow.