Well, I've shot Antarctica and Yunnan & Sichuan provinces in China with the D3x/D3s combo, and Iceland with the P40+/Phase 645DF system. Other than birds in flight, there's nothing I shot in Antarctica or China that I couldn't have shot with the Phase. In retrospect, I wish I'd had the Phase with me on those other trips, and will be bringing it with me to Antarctica when I go back in a couple weeks. I very much enjoy the D3x, and I think it's a fabulous camera. But the top of a Mountain in Nepal? Definitely MFDB would be my choice. Hands down.
Can't understand how you would come to this conclusion. But instead of waffling, let's get down to brass tacks (for the Americas, concrete examples).
Here's a shot I took a few years ago from the top of a small mountain in Nepal (about 3200 metres). I attempted to catch the dawn, so set off hiking in the dark at 4.30 am.
I got a few shots of the dawn, but the difficulties in finding a solid platform for my tripod, and the continual need to wipe the condensation from my lens as a result of the lens suddenly being exposed to a cold environment, after removing it from my camera bag, caused me to miss a few good shots.
Not to mention the complaints from the model because she was shivering with cold. You wouldn't believe the abuse I suffered from that lady, as I stuffed around setting up my equipment.
Anyway, let's do a few technical comparisons. I was using a 12.8mp 5D. The scene was shot with camera horizontal, taking 3 shots for stitching purposes. In fact, the resulting aspect ratio indicates that the middle shot was necessary only for overlap purposes. The resulting composition is very close to just two 35mm shots end on end, ie, 72mm x 24mm.
The lens I used was 30mm at F11 and 1/50th sec exposure.
Let's consider what would have been required had I hauled a P65+ up the mountain.
Could I have captured the same scene with just one shot with the P65+? No way!
To capture such a scene with a 72x24m sensor, I would have need a 15mm lens. The P65+ sensor is only 54mm wide. I would have needed a lens with a focal length of 72/54 x 15 = 20mm.
Is there such a lens for the Phase DB?
Let's assume that such a lens exisits and that we could shoot this scene with a single shot from the P65+. After cropping to the 3:1 aspect ratio, the 60mp of the P65+ becomes about 27mp (54x18mm), which is very close to the 'real' MP value of the 5D stitch. (2x 12.8 = 25.6). The actual resulting image size is about 40mp after warping and stretching, but this reduces resolution somewhat.
I'd be prepared to accept that a P65+ could deliver this result with just one shot, if a high quality 20mm lens were available.
However, here we're comparing old 35mm technology with newer MFDB technology. The comparaison should be between the 21mp 5D2 and the P65+.
In this scenario I've described, the 21mp 5D2 would produce better image quality than the P65+. (42 MP v 27 MP).
Okay! Why not stitch with the P65+? We might suffer a bit more abuse from the model shivering at the high altitudes, but never mind. We're dedicated professionals.
The equivalent of a 30mm lens on 135 is 45mm on a P65+. Instead of F11, we need to use F16 for same DoF. To get maximum image quality we need to use ISO 50. In stead of 1/50th at F11 and ISO 100, we need to use F16 at ISO 50 and 1/13th sec exposure.
Sorry! There's a slight breeze. I know. I was there. That grass in the foreground is swaying in the breeze, not to mention the shivering of the model. A 50th of a second is a minimum. I'd have preferred a 100th. With a D700 I could have used a 100th. A 13th is not acceptable.
Moral of story: Don't carry an MFDB to the mountain top. A D3X or 5D2 is a better choice.
PS. The nude model in the foreground was placed there just to grab your attention. I'm slightly amazed that some posters in this thread do not seem to get the point that this topic is not about which format can deliver the best image quality, but in what circumstances these formats can deliver the best image quality.