I had heard the metallurgy of the P-01 was somewhat improved over past work, same as the Sp-01.
The only "metal" difference I know of for sure is that the P-01 has a forged alloy frame, rather than a cast one.
The SP-01 is still cast steel, like some of the other CZ full-size guns, but some of the grip-dimensions have changed, and it has a longer dust cover and beaver tail. There are a number of other changes with both of those guns, however, that many people like.
That the P-01 is forged alloy might be important to some folks, but the other alloy CZs don't have a reputation for frame failures...