Some observations i did the last years.
With film and a good -drum- scanner it is possible to obtain really very good results. 6x7 and 4x5 deliver much more detail than a 12megapixel camera. However it is difficult to extract that quality out of the film and get it on a print.
Drumscanned, a 6x7 delivered by a Mamiya 7 will be around 25-30 megapixel and i think the difference with a 45mpix back is not too big. I really would test a Mamiya 7 and a P45 back but the 600 euro /day price for the rent is a little too much.
A drumscanned 4x5 inch made with good sharp lenses is something around 80-120 megapixel.
Only very fine detail objects (landscapes) can show the differences between 12 and 30 megapixel. With objects with bigger structures it is very difficult to see the differences. Skin with 12 mp is almost the same as a skin with 30 mp on a 12x16 print.
Both observations are for color slides with about 50-60 lp/mm maximum resolution. With black and white film with 90-100 lp/mm it should be possible to get 2-3x that resolution. In reality it would be very difficult due to less than perfect situations, lens, used aperture, tripod, wind, scanning etc etc. Scanning is a crucial step to get the quality out of the film.
The often used Epson scanners will effectively give you not much more than 1500dpi scanresolution. Your 6x7 slides will effectively be downscaled to a mediocre 12-14 megapixel. The difference with a Canon 5D, Nikon D2x will be gone.
Probably the digital camera will look better in most cases. However, a 4x5 inch scanned with a flatbed will still give you around 40 megapixel, a lot of pixels but less than half of the 100 megapixel a 4x5 can hold. The Flatbed scanner will still make it look soft due to the ccd blooming and chromatic aberrations of the lens system.
CCD based scanners deliver a completely different scan than drumscanners. I think probably the blooming of the ccd's makes the scans soft which can't be repaired with USM.
Look at this wonderful site for the differences between well known scanners.very good compare of various drum ccd scanners.
Even not all drumscans are the same. The best are the ICG's and the Aztec premier.
An (Epson?) flatbed should be used for first impressions and quality judgment of medium or large format film should not be based on it. Not all printers show you the differences.
I send 12 megapixel D2x and 30 megapixel Mamiya 7 files for 12x16 inch (30x40cm) prints to several printers.
Durst lambda, Durst Theta, Frontier 3xx and Frontier 550 printers and Epson 2100 inktjet. The results are disappointing.
The only printer capable of showing a clear difference is the Frontier 550
. Even at this relatively small size the Mamiya 7 prints are clearly much sharper than the 12 mpix Dslr prints.
With the Frontier 550 the 12 mpix prints of the D2x are very clear and nice but the Mamiya 7 prints give you the strange impression to be there again. They are really unbelievable, very sharp. Very small details can be seen on the prints. I went back to the place where the photo was made with the print in my hand and with the naked eye i could not see more detail than i could see on the print.
The Durst Lambda was very disappointing. Almost no difference between D2x and Mamiya 7. I don't know if all Lambda's are the same but i was told the laser had to travel a long distance and that could explain the relatively bad performance for small (12x16) prints. Durst theta is also a very sharp printer. I did no comparisons but the print results show very clear very sharp prints. I am still not convinced an Epson 2100 or alike (3.5 / 4 pico liter) can deliver the same print quality as a new generation laser printers like the Frontier 550. My initial test shows a maximum resolution of about 250 dpi of the 2100.
So i still think that especially for fine work, landscape, b/w the mediumformat and largeformat is unbeatable but in the whole process from scanning to printing only the best products must be used to get good results. Even using the wrong printer can make the results less convincing.
Still even at a small print size of 12x16 inch a well drumscanned mediumformat 6x7 slide of a good camera like a Mamiya 7 and printed with a really sharp printer like a Frontier 550 (570) can look much sharper than a 12 megapixel dslr. The difference is still there.Mamiya 7 compared to Nikon D2x