I have a .25 R5M long and it is well engineered and built tough!
My first priority is that it had to be backyard friendly with my needed hunting accuracy better than .5" at 25 yards and have over 40 FPE. Secondary priorities were weight, length and operational mechanics.
The R5M long with some added foam and felt is super quiet without any add LDC. I haven't tried anything else but a 25 Marauder and it is much quieter than that at a high power level. I don't believe any other gun stock with the same FPE would be as quiet as my R5M. Adding a LDC add cost, weight and length. An LDC isn't needed with the R5M long but I believe any other gun would need one to keep my neighbors happy. It is so quiet I started working on a better pellet trap. Hitting a dirt hillside was too noisy. Hitting a rubber mulch trap with a rubber tile front is much quieter. I have to try some damp card stock as someone on this forum said that was quieter than regular paper.
Does that R5M have any short comings?
Some has complained about hammer noise or ping. It doesn't bother me at all but my hearing is gone and I'm not expected complete silence for the shooter, only near complete silence for my neighbors.
Some has said the trigger isn't good enough. I believe you cannot reduce the length of the 1st stage pull without increasing the 2nd stage weight. A lighter 2nd stage requires you to accept a longer 1st stage
However if you can live with that, I got the trigger to be very good between 1 to 1.5 lbs with no over travel. I would say that is pretty good.
Someone complained about the mag ejecting itself during loading cycle. I believe that is caused by not fully seating the pellets flush or below the mag's surface. I 3d printed a tool to do just that. It makes inserted the pellets correctly and no brainer and easy cycling without any damaged pellet skirts.
Accuracy I don't know for sure because I'm still learning how to use it correctly, but I got a few 0.25" five shot groups CTC at 34 yards. Most recently they opened up a bit to maybe .33". So I cleaned the barrel (very easy to do) and will see if that improves the group size. This was with JSB Kings. I tried a bunch of other pellets they all shot well without any tuning except for Grizzlies that maybe were going too slow. I have read that FX barrels can't do that.
Out of the box no air leaks, very small ES and SD, no regulator creep. That seems to be the norm on some other brands having some run to a Huma regulator.
I was thinking of a Wildcat, Impact or Vulcan as well but chose the R5M because the others would have require and LDC to be quiet enough negating the size and weight advantages of those guns and even cost of some of those guns. I have no doubts that some other guns cycle more smoothly and have even better trigger pulls and accuracy. It all about what is more important to you.