Obviously Shot Placement is key here as well as many other Factors bother Controllable and Non-controllable. But!
All things being equal The Blade with my biggest Cutting Diameter is going to give you consistently the best blood trails. <---thats a period at the end of the sentence.

I personally go with the RM Gator XP I believe it is probably the best Penetrating 2" Mech out there. Not only because of the profile but because of the way the Blades open as well.