For me, the difference between the Purple Hammer and Pitch Black is night and day. The Pitch Black is much more of a traditional urethane look. It digs in very quickly, and the move downlane is extremely smooth and predictable.
The Purple Hammer is even stronger in regard to the dig into the oil, but somehow it still manages to shape down the lane. It's almost as if it hooks twice. Honestly, I've never seen a urethane ball do what the Purple Hammer does. If you have enough head oil, you can actually open up your angles a bit with the Purple Hammer until the backends get sloppy.
That was exactly the problem that one bowler had during the Cheetah telecast from last night. With all of that urethane going down the lane, the backends were bound to soften up. One bowler moved back more to the outside, squared up, and used some of that push oil as hold. Another tried slow-hooking the Purple, and it just wasn't consistent enough. It proves that for as good as the Purple Hammer is, even IT has its limits.
As for the Blue Tank, I've only seen it thrown on TV a couple of times now. It's looked okay at times, but I haven't seen enough of it to truly make an informed statement about it. I'm guessing that's Motiv's attempt at a Purple Hammer, but, again, I'll have to see more of them go down the lane before I can say much else.