I would try an SL first. Its going to be a different mindset and flow of work. I had a Leica kit...I sold it. It was my favorite camera, and the camera that least was able to make the images I am making right now. No fault of of the camera...it was just the wrong tool for me. However, I love the M line for what it was. Rangefinder with excellent manual focus, small, amazing sensor, and great wide angles. I never used accessory finders...I just learned to wing it. At the same time, I felt surprised everytime the images were exactly as I intended. It was a nice surprise...kinda like developing film and seeing perfectly intended exposures.
The SL will bring a different mentality since you are more capable of seeing what you are shooting, and what your results will be. Its a more refined experience I think. You also won't have to deal with rangefinder and lens calibration services.
I dont think one is better than the other...I think Leica just gave their user base a good option for those heavily invested. Especially if you like to shoot really wide, or above 90mm.