I love my mages, they just don't hold up too well in arena (Probably related to My playing, not the mages). For everything else I want to do (BG, World PVP, Dailies, Heroics with a live tank friend)they rock.

But the shammies are wayyy more survivable in 5v5.

Overall i'd say my 4xmage 1 priest group is more fun than my shammies, but since my goal is 5v5 & I personally can't figure out how not to get Roflstomped on them in 5v5, I spend more time on the Shams.