In all reality the No Mercy, No Mercy Beatn, Bite and Anger will all work on heavy long oil. In fact, take a Blue Vibe and bring the cover down to a low grit like 1000 or 500 abralon and it too will work very well on heavy long patterns.
I think your ball choice should really depend on what type of reaction your looking for?
What kind of bowler are you? Stroker, cranker or tweener? This may help us with which ball would probably work the best.
The No Mercy has a very strong mid-lane and hard arcing backend.
The No Mercy Beatn' has more length and backend than the NM.
The Bite has a little less in the mid-lane than the NM (not by much) and a stronger, more angular backend.
The Anger is also a very strong mid-lane ball with a strong backend. When the cover is brought down on this ball the mid-lane get's very strong!
The Blue Vibe when dulled has a good mid-lane and smooth backend. Basically just strong thru out the lane and will not overreact on super dry backends. If you want control then this is the ball for you.