Lambis,
First off, you have some very interesting and nice shots posted....creative and even a bit surreal....very nice.
Now, my thoughts on this are a bit divided, but that is not unusual. If you primarily shoot digital for your other work, that should also be your primary tool for the kinds of things you plan to shoot on your trip to Crete. You will not really be gaining much, if anything, with respect to lowered light/higher ISO, than you might if you shot film. If you max out at ISO 400, they should be about equal performers, but if you plan to shoot higher for available light, then you may get a bit more with good B/W film pushed to what you need. But overall, I think you would get all that you need from the digital back, and do not bother with the film and backs, unless you just want to bring them along or do something special. The processing and post processing capabilities with digital far exceed what you may be able to do with film, plus digital will be so much easier to work with there and whenever you get back. Just an opinion.
Now, for the split thought on this....I always wonder why we tend to agonize over what gear to take or use. If this is a once in a lifetime planned and purposeful trip to capture the things you really imagined, why not take all the gear you could use to fulfill your objectives. As photographers, we tend to collect lots of gear, yet we also struggle to always pare it down to the barest minimum when we plan to travel. Personally, if the purpose of the trip is photography, bring the gear that will get you the results, and if that means both film backs and digital, so be it. If one makes the decision to only shoot digital, why keep all those film accessories? (Yes, I understand that a film back and a few rolls of film are are very effective backup if the digital back goes down and your camera can utilize both backs, but seriously, how may times do any of us really resort to that?)
So, if you are looking to achieve a very specific kind of look that you believe you can only get from B/W film, then take the film and backs, otherwise just shoot the digital back you are most familiar with for shooting and processing and spend your energies being creative with just that kit. You will not be giving up much of anything, except the extra gear, the worries about the film (temps, x-rays, etc.). If you really are not as concerned about the extra gear and weight, I would rather pack a portable flash and reflector to help out for the lighting you are looking for beyond the studio.
Again, just my thinking on this as I too constantly wrestle with these sorts of choices.
LJ