Personally I think the Empire ships would win rather easily (multi teraton firepower vs multi gigaton firepower for cruisers), but this relies on rationalizing the planetary destruction feats in 40K through explosive cores (and hell, there are quotes saying exactly that about them), but others would take a more brute force strictly no magic cores stance which then determines firepower well into the petaton / exaton range per shot, easily surpassing star wars. This entirely depends on the calc set and which sources are used for either, and the individuals rationalizations for the calcs and conclusions came too. However, the IoM brings much more than just plain ol firepower. In a straight slug-match, this matchup can go either way, and then the question of calcs will invariably come up. They will be staffed by the best tech adepts and will be using massive amounts of scrapcode to mess with the enemy computer systems. A Mechanicus Ark is a battle barge/battleship on steroids. They do things like rip moons from orbit to be used as ballistic weapons as well as fire time-traveling black holes. Depending on the Battle Barge and which chapter, a librarian or chief librarian may be present which can do all that and more.ДЈ. Every ship with a decent astropathic choir will be able to do things like stroke out the bridge, read minds, mind-wipe command personal. If Halo Earth's defense are still intact, a techmarine can hack in and use them against the GE fleet.Дў. There's nothing onboard those ships that have any chance of stopping a Terminator strike force. They can disable key ships (eg Executer/Eclipse) ships by teleporting Terminators over. Three things, IMO, tip this towards the IOM.ДЎ.

Star wars galactic marine