First, please excuse me for my poor french-english !
don't hesitate to correct my spelling !
to be honest, i'm quite biased... being a successful arca user for years, and knowing them... i'm naturally in the process to buy a RM3D... but this will be a major investment for me, and i want to make shure that i will choose the right tool for my needs !
in the mean time, alpa's people have being always very helpfull with me, and i quite enjoy the look of their stuff... and i enjoy their website too, when i turn the sound off ;-)
Why considering Cambo as well ? because i have read many reviews from people who found that the Wide RS suite their needs perfectly...
Why not considering the sinar ? because in some occasion, you need to shoot hand held even for architecture... and the artech isn't a part of a system for now...
So, here are my previous conclusions :
if you needs 4 lenses (or needs your lenses to be mounted), and needs a digital adapter plate, a finder, and a good way to level the camera, then the prices from this cameras systems aren't far away each other... but, i'm waiting for precise quotations at the moment.
Considering tilt function : the arca is the only system that can offer it for my beloved 35 XL and shorter lenses (minimum 45 for cambo, and 85 for alpa).
Considering ground glass : the arca can use the expensive rotaslide that provides even more stitching possibilities. So you can compose the entire image with the ground glass, make the focus with the precise focus ring, and stitch with the rotaslide....
Hand held use : the nice thing with alpa, is that you can share your equipment from one body to the others... but both RS and Rm3D are still usable... and with arca, you can use you lenses on a classic LF camera !
Focusing : the arca wins, because of the precision of their own ring... but you need a laser meter... i don't trust their sonar so far, but i may be wrong !
Considering digital back adapters : Being more expensive, the Arca's one still the only one who can be calibrated (shims) for your own back, there's some variations... we are talking about microns !
About view finders, i hate all of them ;-) but now we have the DB sreen to check the final image !
The way the lens is locked to the body : in this respect, i've found the arca to be weird compares to the others.
And finally, being an owner of two f-line camera, i will be able to use my lenses (especially the normal and long ones) as well as the rotaslide on all the cameras !
But, because there is always a but... i hate the arca handles !
Unfortunately, where i live, we don't have shops as capture integration to be able to test things !