I love 50mm lenses for 35mm. It's my favorite perspective and the choice is so wide plus the price usually fairly good. The 50/2 Summicron DR is hands down my favorite. I just LOVE it's character for my B&W work over all others in over 30 years of shooting. Mostly it's the razor sharpness with a nice moderate contrast the sways me----terrific character particularly for casual portraits and such. That said an old-style 50/1.5 Sonnar I recently acquired with a Contax IIIA is proving a close second. And perhaps overall (for color and B&W) it's my 45/2 Planar for the Contax G2 that is one I'll never part with but mainly BECAUSE it's so different than the other two (I know, 45mm is neither a 50mm nor a Summicron or Sonnar, but it's close enough!). And lastly two surprisingly wonderful lenses I also own and use on my Leicas is a black 50/2 Jupiter-8 and a very nice Russian 50/3.5 Elmar-clone. Both are outstanding.

So I'm not helping, I say keep them both. But if it's one over the other than shoot as many photos as you can with both lenses on your favorite film for the next 60 days and see which one floats your boat more often.