About 10 years ago I tried an experiment where I used the same speed settings on a film cameras as I had used on a digital camera. It didn't work - the film was exposed very differently to digital (I don't remember if it was under/over.) The ISO number that you get when you take a picture with your DSLR is not the same as the ISO number used for film. Try it for yourself.
That seems like a difficult experiment to conduct. There would be too many variables to use negatives and actually quite a few variables using transparencies. Did you develop the film yourself? What were the controls used to assure that temperatures, etc., were precise. If you sent the film to a third party to be developed, you lose all control over the process.
The process of developing film is standardised - C36 is "the process" that is used to develop colour film and it is the same process the world over. The only quality impact is the amount of dust that finds its way inside the machine and then causes "spots" on your prints. Differences in paper won't impact whether the print is dark or light due to under/over exposure.
How were the camera's calibrated. Did you verify that the mechanical shutter of the film camera was correct? Film cameras are notorious for the shutter speeds being off. Was it the same lens on both cameras?
Why don't you give it a try yourself?
Buy yourself a cheap Canon EOS camera, something like this:http://sfbay.craigslist.org/sby/ele/4552124495.html
and use the same lens on both cameras with the same shutter and aperture. If you've only got an APS-C camera with EF-S lenses then this might be a bit more difficult/expensive as film cameras are all full frame.