The assertSequenceEqual docs[0] say:
"""
This method is not called directly by assertEqual(), but it’s used to implement assertListEqual() and assertTupleEqual().
"""

The asserEqual docs[1] say:
"""
In addition, if first and second are the exact same type and one of list, tuple, dict, set, frozenset or str or any type that a subclass registers with addTypeEqualityFunc() the type-specific equality function will be called in order to generate a more useful default error message (see also the list of type-specific methods).
"""

assertEqual[2] calls _getAssertEqualityFunc[3] that checks if type(first) is type(second), so in your case no specific assert function is called, and since you are not comparing objects of the same type, you are not able to use addTypeEqualityFunc() either.

I think in this case using assertSequenceEqual() directly is ok.

[0]: http://docs.python.org/py3k/library/unittest.html#unittest.TestCase.assertSequenceEqual
[1]: http://docs.python.org/py3k/library/unittest.html#unittest.TestCase.assertEqual
[2]: http://hg.python.org/cpython/file/124fb2b39ed9/Lib/unittest/case.py#l637
[3]: http://hg.python.org/cpython/file/124fb2b39ed9/Lib/unittest/case.py#l604