I have both,, but my Kirst is in the Colt 36 types and the R&D is in the Remingtons. I would get a Kirst to try in the Remington, except that all my Remingtons are already converted, and $250 is a lot of money for a comparison test. The Kirst has two versions, the one has an ejection port, and an available ($100) ejector rod kit. If you make this conversion, you have manufactured a gun according to the ATF, so it can never be sold. (unless the buyer swears he made the conversion). Also, the ported Kirst is as slow to load and unload as a Colt SAA, one at a time, but you can, with spare cylinders swap them out ala Eastwood, 7 seconds (?) so it's good for both ways. You also sometimes have fired cases back out as you cock the gun and stop the works, they really need a gate in the port. The unported Kirst loads by removing the cylinder, like the R&D. The Kirst has 1 firing pin, the R&D has 6.
The R&D "angled" chambers are not in the least a problem, the angle is so small and the semi-round nosed 45 bullet turns the very slight corner and is as accurate in my experience, as a Kirst, on the target.
The R&D if used in the Colt type requires disassembling the gun to load/unload, so the Kirst makes much more sense in the Colt than the R&D does, even though you have to cut the port in the frame. Note, a friend has 2 Pietta Colt Navies with Kirst, and both guns suffer backing out fired cases and stoppage, I have two as well and neither one backs out (Uberti's but that shouldn't make a difference). His chambers are smoother, and that may be the problem. We are talking about making a gate, and I've already designed it, except that of the 4 units, there are two different sets of dimensions for the port, so they'll have to be individually fitted..
I like them both, and the quality is equivalent, though I prefer the R&D firing pin retained by a threaded bushing to the Kirst, which is staked in and will be harder to repair if it ever needs it.