Well lets compare shall we...
Assuming you would gem your T9 pants with 2 Reckless Ametrines...
-46 stamina (has no value for DPS)
-12 spellpower (this is the biggest loss, however the gains of the other stats will overtake this substantially)
-80 resilience (again, has no value for DPS)
+2 piece tier 9 bonus
This would net you a large DPS gain over the PvP piece.
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.