AFAIK Maximilian was more intelligent than his brother - he had no trouble with learning in school when Franz Joseph had to work hard. (Some people gossiped then that he really was the son of Napoleon II.) He also was more liberal. OK, the times of Metternich are over already, so that wouldn't be the problem. The question is, whether Austria was reformable at all, or whether he wouldn't be successful cutting all the red tape and taking people their old privileges.
Hungary, or even South Slavia, might come into existence as well under him - unless he decides to germanize his people, like Joseph II. Hm, IOTL empress Sissi was promoting the double monarchy - but Max might not need her. I wonder whether the two would still marry. Maybe his mother Sophie (quite a difficult person - she was called "the only real man at court") would be more lenient with him, as he was her favorite. If not, she would hamper a liberalization of Austria.