Yes, I've used both. In the 70's it was Nikon F and Leica M3 for me. Leica, Nikon and Canon were the rangefinder staples of the old time Life and Look photogs.
But where the Leica shines is in close up candid work...shot with the Leica MM.
This type of up close candid work is very hard to do with a dslr. The ergonomics of a dslr are not conducive to it.
You can make a little Fuji 'Leica like' if you slap a manual lens on it. But it is hell to focus. I prefer the rangefinder.
This candid was shot with an old 16mp Fuji.
I'd never use a Leica here. They ruin the cameras. I had someone break off my flash at the hotshoe.
This candid shot below was with a Leica M240...
The other thing is a dslr is very uncomfortable to carry in your hand like I do for hours on end. But from the photography I see, most of the Leica uses like them because of the cult, more so than needing a rangefinder.
This is what a Leica MM does if you take your time...handheld. I heard the newest MM's do better.
I've used all type of cams from Minox to 4 x 5...the Leica style rangefinder is best for my type of work. It will not take better photos than other cams, but it allows you to get photos you could not get as easy if you did not have a Leica / small manual rangefinder style cam.