I have both, and they are drilled for different purposes.  The XD is pin under for an earlier read, while the BD is a 5" drill and gets great length.  They are used for different lane conditions, with the XD being my heavy oil, longer pattern ball.  It just loves the Shark or the Dead Man's Curve patterns.  The BD handles Scorpion or Chameleon really well.

I still can't manage the Viper.  As my Coach calls it, a house shot with a puddle in the middle.  It's just too short for me.  I can't find the right line.

Between the 2, the XD gets a straighter entry angle, while the BD comes in closer to 6 degrees.  The XD holds a line on heavy oil over 13, out to 10-8 and back.  The BD  goes out to 5 and storms back.  The XD reads earlier then the BD which carries deep up the lane.

I have both the Xtreme Damage and the Black Diamond. Both are drilled pin-up for max lenght. My Black Diamond is polished, it rolls out smooth,  when it hits the dry it comes back with a (strong arc). That's the best way to discribe its reaction, pin carry is ridiculous!

My Xtreme Damage is a absolute monster on the backend, to call its motion skid flip would be and understatement. This is hard for me to say do to my love for both these balls, but the pin carry of the Extreme Damage can't be rivaled. The quality of strikes are unparalleled! The best & worst thing is, my Black Diamond, Xtreme Damage, and Buzz Attack can all handle the task. Picking one over the other sucks!
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Fall Arsenal 2009
Terminator
Terminator Rebellion
Buzz Attack
Xtreme Damage (Just Arrived)
Black Diamond
Track Spare Ball