All 50mm's tend to be very good, but the 1.7 Planar is ever so slightly sharper than the Summicron. The 1.4 Planar about the same as the 'cron but with an extra stop. The Leica costs a fair amount & weighs more. R4 has aperture-priority... but it does have a valuable red dot.

I like my 25-year-old RTS, it's solid but works well.