I consider the Summicron technically the best Leica 5cm of this selection - it was and is a stellar performer. Next up for me comes the Summarit 50/1.5, beautifully made and delivers crisp images stopped down a bit. It is unfortunately now hard to find and expensive in usable condition. A coated Elmar is a wonderful choice if one is on a budget and compactness is a priority. The Summitar is a fine lens, combining both aspects of compactness, with quality. However for a little more one can buy a vintage collapsible Summicron which outperforms it.
I find the Summar simply a lens a little too far ahead of its time technically. The images clearly lack contrast and often sharpness. The early 50/2 Sonnars are similar. To me it is a functional collectible, but not for serious work. I prefer an Elmar in this price range and I think the prices on the used market reflect this general preference.