It's kind of hard to say how good Chin's control over his conquered territory was. We saw that he was a brutal tyrant, and we know that after his death his empire collapsed completely. For all we know, the entire Earth Kingdom was on the brink of outright rebellion against him when he conveniently died. Also, Chin and his soldiers were Earth Benders, and as such had an advantage that the Fire Nation didn't right from the start - obstacles that would trouble the Fire nation for decades like the walls of Ba Sing Se would have been no challenge at all for Chin. I have a feeling that if he had tried to attack the Air Nomads, the Water Tribes, or the Fire nation, he wouldn't have had nearly as much success as the Fire Nation did.
So for me, Ozai and the Fire Nation are the clear winners.