The problem with using pve trinkets in instanced pvp is that they are automatically de-leveled to ilvl 496 and all the effects are reduced as well, whereas when you have 2 pvp trinkets equiped you get a dmg reduction bonus as well as they won't be de-leveled like the pve ones. For reg bgs its ok to use pve trinkets till you can get the pvp ones but for rbgs and such you really want to be using pvp trinkets.