The first question that popped into my head is the same that Niika asked. How much of a difference in dps is there between you and the other Hunter, Lady?
My recommendation is don't switch to MM just because "its what everyone else is doing". If you like SV, keep at it. Look in to ways you might improve on your spec. I play MM because I like all the different shots the spec gets, not because its the new "uber" dps spec. Like Niika, I'm a agility MM. The SV Hunter in my raid usually is right on my heels or passes me in dps.
The main difference aside from FA between most MM specs is whether they have Imp Arcane or not, check a spreadsheet to make sure, but generally around 350-400 is a good range to aim to drop Imp Arcane and only use Arcane when moving.