Hmm not sure if that much has changed but from my experience frost was no.1 by far.
Yes you dont have big fire bolt crits ( wich is good in raids you'd rather have steady damage instead of a oops-crit-death kinda mage)
Also iceblock can come in realy handy plus since as a mage your ussually no.1 AoE i think the expanded range , extra slowing effects etc are the most usefull for a raid.
FYI the time i raided with unity 1 frost mage always came in no. 1 on damagemeters, yes indeed not the rogues. I dont think that would have been possible with big crits at all.
It used to be fire that was most commonly used for pvp, big crits is pvp, altho now the water elemental owns arenas. And also quite a few mages go fire now only because SSC is a frost based instance where as you guess the mobs have lot of plus frost resistances.