I have had all of those guns, but have sold the M&P. The CZ-75 SP01 needs trigger work immediately, but will then have the lightest DA trigger pull of the different DA/SA guns I have shot. It is fully accurate. It is narrower than the Sig. Classic sigs need trigger work, but out of the box are better than the other two guns. You can tremendously lighten the DA pull by changing the hammer spring.
I mostly shoot an Sig X5 Allround, which is super accurate and has no recoil in 9mm. It just came back from Gray Guns, and had the Competition action work done. The trigger is now super smooth, but still heavier than the CZ.
The M&P has a terrible trigger out of the box, but with a 25 cent trigger job it will probably be pretty good. Being light, it is fast to draw but has noticeably more recoil than the metal guns you are considering.
If you have medium to small hands, I would go with the CZ but plan on buying a Custom Shop model, or doing the action work. If you want to save money, buy the M&P and do most of the action work yourself. I did put in the Apex parts into two M&P pistols, which helped a lot. However the Sig trigger is smoother out of the box than the M&P was after the Apex parts were installed. However a 25 cent trigger job would probably work wonders.
If I was going to buy a plastic gun, I would go with the new Sig P320 or the CZ P-09. The CZ holds 19 rounds. The P320 has a much better trigger than the P-09, from what I have been told. Actually I have heard it has a fantastic trigger for an out of the box plastic gun. These are both reported to have very light recoil, probably much less than the M&P. That is a big advantage during a training class shooting 600 rounds a day.
Basically if you have large hands, I would go with the SIG. If your hands are medium or small, I recommend the CZ SP-01. My CZ shadow did develop an extraction issue in the middle of a match, and I had to drop out. The Sigs have never let me down.