John A , Jul 14, 2009; 03:30 p.m.
Film and digital work a bit differently with time exposures. Reciprocity doesn't seem to be a big issue with digital, so your exposures should be reduced at the same relative iso speed. I have shot RZ's in the past and now shoot both H and V system Hasselblads. I bought a 1dsmkIII and also have a 5dII. I ran a comparison test with my H system lenses, which I believe to be not only sharper than Mamiya lenses, but also V system Hasselblad lenses (I loved my RZ by the way, my switch was a need for the other features the H system offers). The comparison was at iso 400 film to iso 400 digital. The result, in fine detail, was that even though I might have felt the film has a bit better acuity, the lack of grain made the digital a more usable file and makes it appear a bit sharper. I compared these files at 100%, which was about a 2000 dpi scan of the 2-1/4 film and also resampled the digital file to 3200dpi, the size I scan my negatives. The result was the same in both cases--I use the Imacon scanner for comparison. I don't know that the result would have been the same with 100 speed film vs digital, but I was doing the test for aerial work where I need to use iso 400 most of the time with the MF camera.
My problem with the digital cameras is more that they lose sharpness if you don't shoot them in the sweet center section of the f-stop range-most about f4 to f11/14. Outside this, they seem to start to fade a bit. This might be acceptable to many, if you make smaller prints, but it is not an issue you will generally see with the film cameras. Of course, because you will use small focal length lenses, your need to stop down as far will be reduced with the 35mm lenses.
I carry my digital more now than my film cameras, MF or large, but I still take the film camera as well when I am doing landscape and certain other things. On the other hand, the digital cameras, with their abilities in certain cases, including high iso performance, have opened up areas I used to be more reticent to shoot. So, my thought is really one that you need to see if your use is better served with the film or digital camera--borrow or rent one would be my recommendation.