Dave, Blueprint:
Here's what I saw when I did the testing. I have both balls drilled essentially the same, the only difference is the EPH was 1/8oz illegal on side weight, so there is a small hole about 2" below my PAP. I believe it's a 5/8" bit, 1 1/2" deep. No hole on the Blur Hybrid. Both balls at this point are at factory finish, which Dave correctly points out is different for each ball. I'd thrown the Blur Hybrid for about 15 games, EPH for about 5, before testing.
At this point, I found the Blur Hybrid to go a little longer than the EPH and the breakpoint motion was sharper, but I don't think there was enough difference between the two balls to warrant me carrying both if I had an arsenal of 6. (Truth be told, that's why the Blur Hybrid doesn't have a ton of games on it. I like the motion, but I also drilled a Blur Solid and a Blur Pearl, and as someone that can't hook the ball 30 boards, there's too much overlap there for me to carry all three of those balls with me at all times, so I generally take the Pearl and Solid (which is amazing at 2000) and leave the Hybrid home). The EPH makes a hard arcing move at the breakpoint and keeps hooking after the breakpoint, where the Blur Hybrid seems to be sharper and seems to lay off a bit after it changes direction.
That was Monday night. Tuesday night, I took Dave's observation and used a fresh 3000 pad on both the EPH and the Blur Hybrid. I chose 3000 because 1) it was a good midpoint between the finishes of each ball and 2) I had two new 3000 pads to use. At this point, the Blur got started a bit sooner and was a little less angular than it had been, and the EPH was essentially the same shape as before, just with more control at the breakpoint and it started its motion a tiny bit sooner. I preferred the EPH at this finish over box finish because I liked the added control (misses left tended to roll a bit better and carry, misses right didn't overreact), and the Blur Hybrid was about as useful as box finish (still not quite enough when tugged into oil, I still prefer a bit more of a rounded breakpoint) but lost a bit of the "wow" factor with the skid-flip motion.
So, my conclusion: if you are a lower rev player or like playing up the boards, the Blur Hybrid is a better choice because it will give you a bit more length and a bit quicker change of direction at the breakpoint. Medium and high rev players will probably see a more usable shape with the Eruption Pro Hybrid, and that's my preference as someone that falls into the medium category.
Sorry for the delay in replying!