I saw a breakdown on this somewhere. Can't recall where. BUt from personal experience I have found it is a lot easier to get the kill ribbons and medals on SVER, their guns (once again this is my opinion) are better all around than any others I have used. Also on Valor repairing is very important considering they are always losing (Sorry Valor fans but you know it's true.
) Basically go through the list of medals and ribbons and sort them out from these two categories. Can I get this easier if my team is winning or losing. If it is in the winning category go for that one on SVER. If it's in the Losing category, Valor. Raven has moments of greatness and others that they just sit in front of the cross hairs. As a friend and I say, some days their crack is better and they can just flat out rape you high on speed. So with Raven it just depends on the day. You could win a lot one day or not. Hope this helps with your decision.
Honestlythough, I'm SVER originally and plan on going back to them once I get all the PMC trophies. So I could be a little biased.