Kipoz,
I've had the Rm3di for 6-7 years, and I also have the Factum front/rear module. If I'm not in need of gear-driven shifts and want a smaller camera, the Factum is perfect. So typically, Rm3di is used in studio and when space is not a premium. The Factum has a single direction (vertical or horizontal but not both at the same time slide shift) that is shorter than the Rm3di, but works fine for many styles of shooting. The Factum set up is for hiking and portability. I LOVE both the Arca Tech cameras for their size, versatility and compatibility with the entire Arca range of products. The build quality is impressive like all things Arca. The front tilt is built into body so one does not have the extra cost of having that added to each lens. I feel too many people are overlooking the Arca R camera (probably because it's an older design) and moving to a more electronic version (XT) which is far more expensive as well as the mount for each lens being far more costly, to each his own. The CF shutter in the XT mount lenses and the electronic connection from the body to the lens is nifty...but do you really need that? For me the answer is no, so for the Tech camera I prefer an all-manual setup. I also have an XF which I use when speed and autofocus are needed.
Regarding other Tech cameras I've used:
XT, used it and really like it but questions the significant cost of the lens mounts, nearly double of what Arca R mount cost PER lens
Alpa, never used one or have ever seen one in the wild. Probably the most like the Arca in terms of design/build. Very expensive for an all manual camera. Parts may be hard to get
Cambo, tried it but liked the Arca set up more. Not fond of the bulky lens mounts and expensive tilt mechanism
For the work I do, most landscape and technical commercial work, price aside, my preference is in this order:
1) Arca R. (with the cost savings on lens mounts, you could build nice collection of optics quickly if you were on a "budget" compared to the XT)
2) XT
3) Alpa
4) Cambo