I've been researching for a new tough outdoor phone myself and coming across this thread I started comparing the Duraforce pro and the Z force and this is is what I've found so far. Overall the Z force is the better phone spec wise but I can not find that it is IP certified or MIL-STD-810 certified which is important to me because if I drop the phone in a mud puddle or stream, I want it to continue working. I've read some reviews that the Duraforce screen will work while wet which some screens won't and it is suppose to be able to be submerged for up to 30 minutes in 3' of water and it even has the ability to take pictures underwater. The Z force doesn't have a earphone jack so you have to get an adapter to use headphones of other accessories that plug into the jack. I really like the idea of the Moto mods, especially the projector, it would be nice to be able to hang up a sheet and watch a movie while camping but again I worry about how tough or durable this setup would be, what happens if I drop the phone on a rock. For the price of the mod, I could buy a separate mini projector that I'd keep protected until use. The drawback for me on both phones is a removable battery. I have a Casio commando (which is discontinued, too bad) that I really like but it's outdated, slow, and the screen is small but it could take a beating and with it I always carried a spare battery so if I were away for a few days or something like getting lost or an accident happened I had phone power( I know I could carry a power pack of some kind but a spare battery was more convenient for me). There are other tough phones out there with all the stuff I want but unfortunately I'm kind of stuck with Verizon because of a family plan and where I go the coverage sucks for other carriers.
One other thing that has kept me from buying a new phone yet is the ability to root the phone. I haven't done enough research on rooting the Moto Z force yet but with the Duraforce pro since it is fairly new and not a real mainstream phone I can't find any thing on a reliable way to root the phone. Can't really comment much about updates but Moto being a more popular phone brand would probably get them faster.
So in short the Z is a better spec phone but the Duraforce pro is a tougher phone so it depends on which you want.