I bought an absolute gem of a Retina IIIc the other day. It's almost too nice to use, and cost me less than $100. I think it's unlikely I can find a Barnack Leica with a lens in such condition without a lot of luck.
As long as you only use the 50mm lens, the Retina has a lot to recommend it over the Leica, including flash sync at all speeds and the integrated viewfinder/rangefinder.
Something about the Retinas makes me smile. They seem so cute and fun.