Thank god the sorc savant PRE seems balanced now.

You play an ARCANE (sorc/wiz) because you enjoy playing the most powerful class PreU9 or PostU9.

The most powerful class with the most powerful CC ability.
The most powerful instant death (Finger/Wail) which dominates all sub lvl 20 quests and raids (shroud/vale etc) and will dominate epics in U9 (circle of death, power word kill).
The most powerful "convenience" abilities : Teleport, Greater teleport, haste, Jump, Invis, Featherfall, DDoor, shadowwalk etc.

You play SORC because you appreciate the advantages vs a wizard
Double SP From SP items
Faster casting animations
Much shorter spell cooldowns than a wizard
CHA based caster class with powerful UMD
Capstone with +20% DMG

You play a SAVANT because you appreciate the free and balanced special abilities
Cheap SLAs for sustained DPS during red named fights for all the people that cried that they couldnt do anything. Now you can rotate spamming 3 keys every 8 seconds (or however long for each of them).
Free non stacking curse for a bit of a dmg boost ON TOP OF YOUR 20% CAPSTONE.
Free "perk" Abundant step/knockdown immunity / earthgrab ETC.

Weakened in 1 element - WHO CARES you have THREE Other elements PLUS Force. Sorcs u9 have only fire/cold.