I have a Pinarello FM1, I used to have a Cervelo P3C, and P3SL so I can give you a direct comparison.
The Pinarello is a much better bike in my opnion. It’s stiffer, the carbon is structurally better (Toyaca 1K), and it handles like a road bike, so you feel very confident riding it on all courses, whereas the P3C is great in a straight line but a liability on a technical course (remember Dave Z in TdF 05?). Don’t get me wrong, the P3C is a fantastic bike in a wind tunnel, and as aero as you like, but it doesn’t handle anything like the Pina does (or Trek TTX for that matter).
For those looking at Pina for triathlon, Cameron Brown rides a Pinarello FT3 (not the FT1), which is the triathlon frame using the same 1K Toyaca Carbon as on the Prince and FM1… Cameron used to ride a Scott Plasma before he got sponsored by Pina, best check with him his thoughts on those 2.