Full Campaign gear is mathmatically better then the recruit set in PvP in 1v1 situation. As soon as it becomes 1v2 (or worse) Campaign starts to fall behind by rather large amount. As PvP is very rarely 1v1 you are almost always better off going with the recruit set.
Caveat: Once you get to 1000 to 1100 expertise swapping out PvP gear for Campaign/BH gear is beneficial as long as your expertise stays above 1000.
For Pve I use this:
Campaing/Rakata/BH > War Hero > BattleMaster = Columi > Tionese > Recruit
Can you go into more details on why expertise would be more beneficial for 1v2 over 1v1? It's the same bonus and same damage going in and out so I don't quiet follow where the change occurs.
Or at least link a source that could explain it?