In Django (if you use the default settings) example.com/foo will redirect (and thus be equal) to example.com/foo/. This is however not the other way around. These notations don't differ that much, so we shouldn't separate between them in my opinion. To add to this, I think URLs ending with a / are more beautiful.
Apart from what you consider beautiful, there is no technial reason. Django, with default setting for APPEND_SLASHES, will redirect to %s/ if %s is not found; no more, no less. This situation only happens when you use hard-coded URLs, or manually open a URL that does not exist and forget the trailing /. Even then, it does not matter — the only point where it matters is SEO (which the docs also point out explicitly). In the case where URLs are only called through links in the app, with URLs generated by reverse-mapping, nothing ever happens that has to do with it. Thus, this is exclusively a cosmetic issue.
Also, ending with a slash is only correct for collections (i.e. URL namespaces that have sub-URLs for single objects, etc.), not for leaf URLs, imho.
Dropping from the milestone and tagging refactoring/non-technical.