I've been doing a little digging to find out which would the better option to use an offpiece, with alot of high end mages now shifting towards Fire and my guild is at at level where I'm starting to gear accordingly- there has been mixed reception on which pieces to use overall, optimising a BiS for Fire has proven a little tricky when trying to avoid using hit gems to get that cap- with ruby sanctum around the corner and the potential pieces - thought i'd get your opinions on what would be the ideal choice.
Gunship Captain's Mittens
http://www.wowhead.com/item=50663
Plaguebringer Stained Pants
http://www.wowhead.com/item=50694