Good question! It is one I'm researching into myself as a few months ago I came across an image of the P-01 and immediately loved it. The main difference between them is that the P-01 is a compact (Decocking Lever), and the SP-01 is full size (with Manual Safety). Also, to quote from the CZ website:
Originally Posted by Alpacino
"Borrowing from the improved grip geometry of the CZ 75 Compact P-01, the SP-01 utilizes an extended beavertail to protect shooter’s strong hand as well as allowing for a deeper and more secure grip."
Check out the CZ thread here, as I'm sure people have talked about the SP-01 a bit. Unfortunately not too many people discuss the P-01.
I'm still trying to find a store which stock the P-01's so I can have a physical look and feel. The only thing that puts me off the P-01 is that it is a compact. I am really after a full size piece. But like Baldy said, I don't think you can go wrong with either model. CZ make good quality pieces and are very underrated.