Which Sinar is better, P or P2 or P3?
All the info below is off the top of my head, but I am sure Edwin or someone will correct me if any details are wrong...
The P is the original, that was invented ¿half a century? ago... it is silver (aluminium), and does not have individual knobs/thumb wheels for each movement, but has a changeover lever.
The P2 was invented 10 or fifteen years ago, is black and does not have the change over lever, and has a knob or thumb wheel for each movement.
The P and P2 are 5*4, 5*7 or 10*8 inch sheet film cameras, but can be used with roll film backs, scan backs or digibacks.
The Sinar 5*4 lensboard is a long-established standard, and compatible components can be acquired inexpensively.
The P3 is a 6*9 cm medium format camera made for digital - most of the available components have connections for digital, and are not cheap, but it is a marginally lighter, and much less bulky system.
The P was, and the P2 and P3 are no-compromise professional (studio) cameras.
The P is cheap, and has geared movements.
The P2 is about £1,000 on eBay, and you can use it with digital backs with an adaptor and/or stitching back.
The P3 is the best, but is not cheap, and is not widely available second hand.
The F3 is a medium format monorail without the geared movements... it also lighter and takes up less room in your gadget bag for landscape photography
There are other models like the Sinar X, with which I am not familiar.