|EOS 5D, Sigma 50mm f1.4, DxO Optics Pro|
First off, consider black and white photography in general, with no regard to what type of camera was used. A great B&W photo would be a piece of art produced by a photographer who has learned to really see the world in black and white, and know all the ins and outs of creating an image based on this way of seeing. But otherwise, we digital photographers have so many options available to us from the single device, including B&W among the many, we tend to do things in reverse - we always take a colour picture, and later, during a review of the pictures we've taken, might have an inkling that "hey, this one would look great in B&W" - and with a single mouse-click, or tap of the touch-screen, we can turn it into B&W and then back again.
A case in point from my own files - let's make comparisons between the photo above and this one:
Yes, these are from exactly the same Raw file, and I simply processed one in colour and one in black and white - on a hunch. But now that I look at them, I can see they almost are conveying two different stories. In the colour version, I notice the rich brightness of the colours, and especially am grabbed by the reflected colours - so it becomes more of a "compositional piece". The colours make for a very busy picture, and my eyes want to wander all over the place, to try and figure out what this photo is all about, and am left with the conclusion - "this portrays an intersection at night, with a nice looking old church building, and the traffic lights are caught in that rare moment when they're red in all directions, including the walk-lights".
The B&W version is quite different - first it is far more serene, and I more readily notice the complete absence of traffic, suggesting this might be very late at night. Then the second thing I notice is there are two people walking with grocery bags, in opposite directions - a fact that is almost lost in the colour version. Finally, because the colour of the traffic lights is not seen, it must be imagined, but it is readily seen that the walk lights are both "red-hand" in all directions, and yet, the pedestrians are still walking anyway, which further re-enforces the feel of a very late city night, because they're walking / had walked against the traffic lights, so obviously they felt no danger from any nearby traffic.
My conclusion - the B&W picture succeeds at every level, stimulates the imagination about what is actually going on in the photo, and puts the mind in a calmer state. With the colour version, I'm more inclined to merely admire the bright neon colours and reflections, but little else.
Does digital black and white have to take a back seat to anything at all? Not really. Perhaps if I were using B&W film with real darkroom processing, I might have had more impact in my picture, but I don't know that for certain. Not long ago, we tended to view digital B&W photography as "simulated" or "emulated", because of the fact that the "true" picture exists only in colour, and to make it B&W, we were somehow faking it. But technically, although true, does it really matter? Our better cameras - the ones that provide Raw data output, can be made to look like anything now, and the same holds true even for film put through a digital workflow via scanning. If we scan B&W or colour film (it doesn't matter!) to a TIF file output (or in the case of the very best scanners, a DNG output), there is enormous flexibility available to produce a great B&W shot from the original negative. It's not cheating, or faking, simulating or emulating anything, and in my mind, this kind of eliminates the need for a dedicated digital black and white camera, like the Leica Monochrom.
It helps tremendously to have the low pixel density of an older "full frame" 35mm DSLR, such as the Nikon D700 or the Canon EOS-5D Mk.-1. Cameras like this, which are no longer produced, have such a great signal to noise ratio, B&W conversion can be so much more successful, with very little risk of noise sneaking in during the process. It might also be economically viable for some to have these older cameras modified far better B&W by having the IR filter removed from the sensor. Although this is usually done with Infrared photography in mind, it's also great for B&W because it will let more light into the sensor, and for B&W, the nasty colour artefacts which the IR filter is supposed to eliminate, won't matter.