The differences between json and simplejson Python modules are as follows:-
Actually, the json is also a simplejson, which is added to the stdlib. The json was added in Python 2.6, whereas the simplejson was added way before json, that is an upper hand, so the simplejson was added in Python 2.4 for the first time.
The simplejson is also updated with Python, so you can easily access the latest version.