How many Python REPL's are there for Emacs and their relative merits?
What OS have you tested them on?
How long have you been using them?
What version combos of python/emacs/ repl integrating software have you used and the problems you encountered.
I would like to hear your experiences.
This thread How do you create a robust Python IDE with Emacs (as the Text editor) is about creation but does not compare and does not use the string REPL even once as I tried now.