Hmmm, okay, what they have in common (for me) is solidness and some 'body', a certain sweet way of swinging, and they are both slightly demanding. I agree with others that the control is a bit better and more uniform on the PP. The grip shapes though are very different. I also felt the 6.1 (open pattern) was maybe a bit more spinny and that you could access the big power perhaps slightly more easily. Finally, I found the PP generally a bit more consistent and reliable performance-wise, whereas the I found the 6.1's a tad more erratic, but also maybe a bit more off the cuff, and as I said, capable of producing oomph a little more effortlessly.
I've played with most of the 6.1's - PSC and N95 were my best. Also thought the BLX was very good as well. Played YTPP, MGPP (briefly), and a pro-stock PP. Marginally preferred the latter. To be totally honest though, these frames are just a little out of league.