Its more of a personal preference debate.

"Whoever said the pen is mightier than the sword apparently never met automatic weapons."

They both say stuff when you dial the red buttons and press hard enough.

"Munchkin: One who, on being told that this is a game about politics and intrigue in 17th century Italy, asks to play a ninja."
— Andrew Rilstone

I beleive the B5 universe would have the greatest chance for success against the empire. Even if it was just the Earth Alliance against them. With the First ones and the league the empire would have no chance.

Given that an Earth Omega class destroyer is almost the same size as an ISD and given the Omega produces less power, 101,408TW in 3 weeks. It's cannons are far superior in terms of power to that of federation ships, with a max output of 11,989TW, 2.8Megaton bomb, aprox 1/2 the strength of a turbo laser. The Omega could also use its jumpoint as a weapon, opening it directly on the ISD, the energy from the jumpoint would tear the ISD ship apart.

The Warlock class destroyers new to Earthforce have 2 railed partical beam cannons, one of which alone is capable of levelling the United kingdom with 1 shot.

IF you were to include the Vorlons, shodows and other firstones into the equation the empire has no chance. The Vorlon planet killer is far smaller and more manourerable than the death star, comprised of an organic hull that learns from combat. This alone could take on the deathstar as it can destroy entire planets too. The shadow death cloud not only can engulf entire planets and destroy them from the inside out, it can swallow whole fleets and hold them there, inside the cloud the ships exteriors will begin to freeze, requiring the ships to draw more power to life support to keep the crew alive. It can also use its missile which burrow into a planets core to destroy the ships inside.

Lets not forget the greatest weapon ever, the shadow battlecrabs beam weapon. It would slice through ISD's like paper. The beam alone is theorised to have been able to turn entire planets into wastelands and slice up smaller planetoids.