"More successful" here obviously means that their empire lasted a longer time, since that's what we're discussing. They may have been less successful in other ways. I don't really see what my feelings have to do with the discussion.

The Macedonian Dynasty in the Byzantine isn't quite comparable to Chinese dynasties. In China, a dynasty change, AFAIK, meant that one group overthrew another group and established their own nation, with its own laws and government structures. In Byzantine the change to Macedonian Dynasty happened as a result of internal politics (+ assassination). The nation remained the same; just the guy in charge changed.