I have all three (thanks Shawn and Chad at C300), just like the above guys, the Bully is a little smoother (I'm gonna shine this ball), doesn't read the dry as quick as Big Bully.
Big Bully is really nice on fairly heavy oil, have used it in a regional, worked pretty well.
Backyard has a ton of back ends when they are clean. This ball doesn't like carry down too much. Have seen a couple guys throw this ball scotch brited, still more length than the other two, sharper break point, but handles a little more oil/carry down pretty well.
If you are only going to have two, get the Backyard, it is the most different than the Big. Big and Orig Bully may be too close for some to justify having both.
Hope this helps ya....
--------------------
Mike Austin's Precision Pro Shop
Houston, TX
Drilling and Tech Advice BirdDogbowling.com
Driller to many "Stars" and Tony Melendez too!