Here is a brief interview with Virrem, one of the best mages seen in the 39 bracket, Cyclone EU.
Question 1: DO you prefer SP or mana and why?
Uhh... balance maybe. Either you die instant, or you pwn the opponents. The key is not in the damage, the key is in the control. The jump from 200SP to 300SP is negligable, being able to survive long enough to pull off heavy burst.
Question 2: If you had 1700hp do you think you would be effective in arena?
(Lots of laughs) No...what if a hunter or a warlock pops up? Or a fucking priest? You'd die instantly. You cannot do anything with your spell power. Even with 500SP you cannot 1 shot someone, but with 1700hp, you can get 1 shotted.
Question 3: What is the main role in arena for 39 mage?
Control. But you cannot manage to win, with only control - this is not the 19 bracket.
Question 4: Do you agree that more SP = more efficiency with mana.
That depends on the setup. If you are a mage/rogue, you don't need all the mana, and take the extra damage. But if you play priest/mage you need more balance stats.
Question 5: What is more important in arena for most setups, Stamina or intellect?
Fucking stupid questions. I don't give a shit about my stats. I just pwn.
Question 6: Do you notice much different in damage, if you stack spellpower or not?
I've seen many mages stack very high SP, the damage is not so different, and you die too quickly either through outright burst, or using your mana for survivability, going OOM.
Thanks for your time Seargent Virre Twink (retired wow player).