In small format, I used Minolta MD Rokkor glass until I reached a point in life I could enjoy a Leica experience. I bought the older optics as I shoot B&W. A fat 90mm Tele (flair), 50mm mint collapsible 56 Cron, and asp Elmarit-M 28mm f/2.8. The fat Tele will flair if pointed to bright sky....but it is so small and renders B&W contrast just right. The Leitz 50mm collapsible has a fingerprint for portraits similar but different from a Rokkor 58mm f/1.2. Both have great bokeh. The Cron has a circular iris and some images are stunning in a smooth/sharp way. I love this little lens. The 28mm Elmarit-M hands down is better in flair and sharpness than the 28mm Rokkor f/3.5. I got the Elmarit-M for that very reason after a disappointment with the Rokkor.
The asph Elmarit 28mm f/2.8 is by far my most expensive lens. It is very small compared to earlier 28's and can be shot wide open. It serves a specific low light purpose in my kit. Also, should hold its value as a digital crossover. If you are looking to save, the CV 28 f/3.5 would be a good choice and one I would make if only shooting in daylight.
The image quality is arguably compatible between fine lenses of each major brand. M mount Mandler designed optics are small and have wonderful contrast for B&W. I don't think Leitz glass makes better images. It takes the eye behind the lens to do that.
One last thought....we just rent the nice things in life....use them, have fun, pass them on for the next person to enjoy.