I have shot both. I also own a Kahr p380 and had a Keltec p3at that is similar to the Ruger LCP. I sold the Keltec.
The Kahr absolutely blows the Keltec and Ruger away in performance. It's trigger is lighter and shorter allowing you to pull the trigger smoothly even if you stick your whole finger in the trigger like you may in an emergency with such a hard to grasp little gun. The trigger feels closest to a good j-frame, but much shorter in pull.
The grip is a little fatter making it much nicer to shoot than the LCP. It's sights are quite functional and I can head shot at 10 yard easy. Can't do that with the Ruger, or especially the lame Keltec, when under stress.
Recoil isn't bad. Actually kinda weak. Because a combat grip puts my support thumb in front of the short barrel, I use a teacup grip. Basicly a one handed grip with my support hand under the strong hand. I could just fold my support hands thumb down. But a proper combat grip is so burned into my head I'll accidentally stretch my thumb forward and char it. So I try to remember "one hand grip only" when shooting these little guys. Due to the ammo shortage in .380, I don't get tired at all shooting this gun. I put 100 rounds down range in one trip, and felt nothing. (Well, nothing compared to the workout my G23 and 5" 1911's give)
It likes stronger ammo the best. WWB feels weak, and may not feed well due to it's weakness when the Kahr is new. Zippier Corbon Powerball works 100% in mine. If you can find +p for carry, get it, the hotter ammo offer far greater reliability in the Kahr, but i wouldn't shoot that all the time. Kahrs aren't built like tanks.
This is the only .380 I'm confident shooting. I haven't tried the Sig. My keltec p380 was junk, sold it, too much recoil, too many FTF.
I made a IWB and OWB holster for it. The OWB works even under a t-shirt. It's a mini RCS copy I made. Not done with the IWBone yet, needs a forward wing and I'm waiting on 2 Crossbreed clips. (ordered with a supertuck for my Glock23)
I originally wanted a S&W J-frame M&P 340. But Its trigger was too long requiring proper finger placement that i can't promise under stress. And the J is larger, and way slower to reload.