I bought my first Leica RF in 1953 and first SLR in 1963. Since then I've used whichever is most appropriate. Obviously the SLR excels for closeups and long lenses. For most other photography, I prefer the Leica rangefinder's handling and performance. If I could have only one system, it would have to be the SLR because of its versatility. There is little practical difference in optical performance between my Leica and Nikon systems. Both companies rarely produced prime lenses that were not excellent. I have attributed rare unsharpness to the SLR mirror. A rigid tripod or appropriate shutter speeds prevents this. My Leica M4 and its five lenses have given 41 years of reliable service. Nikon F1 and Nikkormat bodies have occasionally failed.