They look like those used on the 999/749R to me, albeit Ducati fitted the silver coloured model other manufacturers fitted gold or grey. These are M4; Though I got them from an Aprilia dealer and they're gold coloured IIRC, Ducati fitted the grey ones to 1098 etc.
So how do the M4 and P4 differ? Piston size? Fluid path diameter? Obviously the Calipers on my bike which have been identified as P4s have a combined banjo and Bleed valve where the M4s in the image above have them separated.
I think the difference is that P4 are machined from billet whereas M4 are cast? So the P4 cost more to make and therefore were only fitted to 'R' models etc. whereas the M4 were mass-produced/cheaper and so made it viable to use them on more bikes. Don't know about pistons size etc.
That’s a big question - depends on one’s definition of “better”. Personal experience: I have/had P4 calipers on 2 x 749R and also fitted some to my M1100S to replace the utter shite standard calipers. I always loved the power and feel of the P4s on my track 749 (with HPK discs and Performance Friction PF95 pads) but I found that they just gobbled up the teeny pads meaning I had to replace them very frequently. These pads are fairly pricey so I swapped them for M4s a couple of years ago - mainly for cost/maintenance reasons. Although the M4s have great stopping power, the feel is not as sublime as the P4s.
