I frequently see mages asking, "Which Meta Gem is best?"
Chaotic Skyflare is the obvious choice, but for some reason people seem to find reasons to investigate the others.
Once again, I'd refer you to RAWR (see Should I HIT Cap?). Since, technically speaking, the benefits from each gem can change with your spec, you might want to see for yourself.
Within RAWR you can assign varying gems to the head-piece with the meta slot. Then you can compare the DPS for each configuration side by side (actually, stacked horizontally). Then you can see for yourself exactly how much each meta gem is worth to you. Just remember that with RAWR you have to configure the fight correctly to match what will be happening in your raid (fight length, raid buffs, etc.).