If you're unsure, you can try one out and use the reset quest to reset them all. What I did to help Octavia figure out was the best, was I searched her log file for all the You begin to cast (or whatever the exact phrase is), and then sorted that list by the spell name, then used excel to count them up, delete the duplicates, then looked up the spells and put down what type of spell they were, then sorted the list by spell type, and added them up. It was clear for her that Alteration was the way to go, but she was usually the primary healer, and did alot of buffing and porting as well.
For Druids Alteration is the largest number of spells, but again, if you solo alot, you may want the Conjuration. I guess it also comes down to what you want to save mana on the most.
In a rush at the moment, so when I get some time, I'll add a link to the specialization reset quest.
EDIT: Respecialization Quest
Hope this helps some, and doesn't make you more confused.
Yther Ore. Edited, Dec 29th 2011 2:30pm by Yther