The Rebel Alliance has a great chance. Things like a Mon Cal crusier(MC80 or above) could easily defeat any ship in Revan's Empire. The Rebel Alliance also probably has more people because they have a greater number of planets. I think the Rebel's can take this do to more resources, better technology, and because of Ackbar(who I think is around Revan's level in tactical skill).
The Rebels had several thousand ships. Revan has no advantage in numbers. A single Mon Cal(MC80 or above) could take two of the Leviathan, maybe six if it was one of the heavier ones(aka. MC80A and up).
The Rebels also have a huge advantage in the amount of able bodied soliders they have. Remember that the Alliance spans thousands of worlds.
The Rebels also have far greater starfighters. Revan's don't even have proton torpedos or shields, making them easy prey for Rebel ships.
Added with Ackbar's uber tactical skill(which is on the same level as Revan's) and the Alliance defeats him.
TJ, super-conducting armor is far weaker than shields. There is a reason they switched to shields over it.
Also remember that pre-Empire ships had lesser fire rates on their turbolasers. It was Imperial designers that came up with a high speed turbolaser with the same(or on larger ships) greater firepower to former turbolasers. The Rebels copied Imperial technology in their ships, giving the Rebels an advantage 3-1 over any of Revan's ship of equal size, even greater when you count things like the Leviathan being 1/6th the size of Home One(the Rebel flagship).
In result, Revan's Empire is pwned.