I'd take a Canon 50mm 1.8 over any Leica lens you could get at the same price unless you are specifically buying for the compactness of an Elmar (which is about the only Leica lens you which regularly sells in good condition closet to that price). Its very well balanced on a Canon P as well.
I'd also take the Canon over a FSU lens unless you can specifically test the FSU lens before buying. They can be excellent - I have a collapsible Industar which is close enough in performance that I don't have a need for an Elmar. I had a Jupiter 8 which was excellent but it took me 3 purchases to land on one that worked well and focused correctly. That was an excellent lens and at time I wonder why I moved on to anything else. If can can pick up one which has been tested with Leica and you appreciate the results, go for it.