The stormrage is ~7 points better on the ThinkTank rating scale. It's significantly better on Feral By Night's weighting scale, due to the higher priority on expertise. I'm sure rawr agrees as well, I'm just too lazy to fire it up.
Slap them moose horns on boy! The extra damage you deal with head butts is worth the price of admission alone.
...
Okay but seriously, I would keep the tier 8.5 if you had the 4 set bonus and weren't ready to switch out a few peices for t9 equivlent stuff, but if that is not a concern then definatly Stormrage.
I'd take it regardless of the 4pT8. It's a significant upgrade in every stat you want, and 28 seconds of SI isn't that good in most fights - and the fights it is good on (Gormok mostly) don't warrant losing all that stam, agility, and armor.
