Being an owner and user of both Kirst & R&D, I feel that the Kirst is the better choice. If you are a do it yourselfer it is a much easier installation. In addition the tolerances are more forgving when installing and using.
My arsenal includes 3, 1851 Navies in 38 Long Colt, 1, 1858 army Remy in 45 Long Colt and 1, Ruger Old Army in 45 Long Colt.
An example of the tolerance is on my R&D 38 Long Colt if the crimp is a little to heavy they will not fit into the cylinder, on the other hand the Kirst again is more forgiving and slips right in. On my 45 Long Colt the R&D will not accept the 45 Long Colt and the 45 schofield without modification, the Kirst will accept both without a modification.
Accuracy seems to be about the same and is dictated by the quality of your revolver and your expertise at using it.
As far as quality goes they are both extremely well made but for overall use and convenience the Kirst Gets my vote.
Hope this helps.
E-Mail me or post again if you would like more specifics.
Warbucks16