I finely got to compare the R51 to Ruger's LC9 out on the range. My wife and I did some range shooting, she uses a Ruger LC9. We were using Federal ammunition 115 grain FMJ Target rounds.
My wife shot off a 2 magazines with here LC9, and I asked her to try out my R51. She picked it up and said it felt heavier, after she fired off some rounds, she said the recoil felt greater than the LC9. I tried the LC9 and have to agree with my wife that the LC9 does feel like it has less recoil than the R51. I'm not sure why this is. She also liked the smoother back strap on the R51, but thought the grip was too wide for her hand.
The LC9 has a smaller harder to work slide stop lever than the R51. The safety on the LC9 is very hard to work and located in a hard to reach area. The LC9's magazine release is smaller and NOT ambidextrous. Trigger pull seemed much too long with the LC9, but then the R51 had a shorter harder pull. The LC9 does have a much better chamber indicator, you can see and feel it, where the R51 has a hole you must look down, not much good in dark or poor lighting.
Both guns handled and worked great. They both have some good and bad points. We both shot about 75 rounds each.
I had one small problem with a pin that wanted to come out. It's the smaller of the two pins to the left/rear of the QR code on right side of frame. That's that square made up of dots, you can scan it and its gives the model and serial number. My R51 seems to be working better the more rounds I shoot.
Hope this non-pro review is helpful. It's the second time I wrote it, I had it all wrote out the first time and forgot that the bard will log you off after 60 minutes and lost everything I typed in.