I'm looking to buy a mechanical film camera as a backup to my digital camera. I don't need anything electrical aside from the metering, so the shutter has to be mechanical and has to work whether I have a battery of not. I'll be using it under the same conditions as my digital camera (and then some), and it has to be light enough that I actually take it along. Here are some trade-offs I've already done:
1. SLR vs. RF: I do realize there are advantages to RF cameras (no mirror vibration issue, light, quiet shutters, better lens quality), but the price range of RF cameras is a bit beyond what I'm willing to pay for a backup camera. I'd love to own an M3 some day, but I think for this purpose I'll stick with an SLR (unless someone has some other, less-than-$200 RF suggestions). For what I do photo-wise, I think an SLR is also a better choice in any event.
2. Canon vs. Nikon: I don't think I have any significant loyalty here one way or another, recognizing both brands are about equally strong for mechanical SLRs. I do have a stash of some Canon FD/FL lenses I'm using for my m4/3 digital, which has some cost advantages to staying with Canon, but I don't want to preclude going with a better choice if that means getting a few additional lenses.
3. Canon FTb vs. Nikon FM2: The FTb is Canon's all-mechanical SLR that I think will work for me. It's fairly inexpensive as a body, has an MLU, and fits my existing lenses. On the other hand, the FM2 comes with a faster shutter (1/4000 vs. 1/1000), is lighter, and has interchangeable screens. Both seem to be built to last, so that's a wash. As downsides, the FTb weighs 200g more than the FM2, but the FM2 costs more and doesn't have manual MLU.
So, do I choose the less expensive, heavier camera that has MLU and a slower shutter, or the more expensive, lighter camera that has a faster shutter? What should I consider when I make my decision?