You buy one of these as an elective, something you want to use and I'll agree that the Pentax for the price is pretty cool, though there is a difference between the way the cameras feel in hand.
I've never held or seen a 645Z though tested the 645d and obviously the Leica S2.
I liked the Pentax but there is just a difference that is hard to quantify and at the time the 645d didn't tether well, but if it had, I still would have bought the Leica.
Sorry for the cliche, but to me the difference is Japanese efficiency vs. German craftsmanship or something like that.
There is probably no logical reason for either the Leica or the Pentax. Clients won't ask for the resolution, most won't know if there is any difference on set than a Nikon or a Canon and obviously what's in front of the lens is definitely more important than the camera.•
The real difference between the two is the lenses and not just leica glass. With the Pentax the newer glass is not necessarily cheap, or you have to search out a lot of used glass (and usually test them) to get where you want to be.
The Leica allows full functionality with Contax, Hasselblad H series and two versions of Leica glass, so with the H series and the Leica CS lenses you can have a central shutter or not, either economically or at nose bleed prices . . . your choice.
Though when it comes to price, neither are cheap, but then again different usually comes with a premium price in any product.
•The only still cameras we use that clients seem to notice is my older contax and phase backs, especially with a waist level finder. Honestly the last session I shot with the Contax the clients at first asked if I was shooting film.
It is interesting that either due to the form factor, maybe it's just my mindset, but with my Contax I tend to shot more static, with the Leica more fluid, though the final quality of the file from my p30 to the S-2 is virtually identical.
Both are ccd's and not to start a chart/dxo/moire crop war, I like the look of the ccd cameras I own better than the cmos cameras, so whenever the the 007 comes out, I'll probably be one of the last people to try it.
IMO
BC