They both return raw tuples, which are not very intuitive to interpret:
>>> email.utils.parsedate_tz("Wed, 15 Sep 2010 09:53:50 -0700 (PDT)")
(2010, 9, 15, 9, 53, 50, 0, 1, -1, -25200)
It would be much better if they returned some kind of namedtuple, which would preserve backwards compatibility but with much better readability and usability.
Note that parsedate() could also return the existing time.struct_time type (which is compatible with a 9-tuple):
http://docs.python.org/library/time.html#time.struct_time