40k is horribly inconsistent, but using the upper range of conventional starship firepower (easily boiling oceans away), both universes are similarly matched. Star wars tech, despite its very utilitarian and mundane appearance, is canonically incredibly powerful compared to most mainstream scifi
if you're going to make outrageous claims like
>star wars tech doesnt work against void shields becuase they've never seen void shields
and similarly autistic complaints, fuck yourself
so with matched conventional presumably similar defenses in conventional warfare to the imperium, the empire's advantages include
>star wars
-infinitely more reliable FTL, FTL is generally faster, barring fluke warp shenanigans where things arrive before they left, star wars ships can cross the galaxy in a matter of days
-massive industrial capacity, actual research, understand how their tech works, can make new ships
given that the imperium with their psykers are routinely overcome by incompetent soccer hooligans, psykers dont seem like a huge advantage
empire would probably beat the imperium due to the massive logistical advantage
tau arent particularly better than the imperium at conventional warfare, and given their miniscule size, the empire would crush them through numbers alone
eldar, tech is superior, but the numbers once again put the empire at an advantage
tyranids, I can't see the empire winning this, though they did beat the vong which are somewhat similar in their massive numbers, organic tech, and terraforming predisposition
necrons, fluffwise, tech is too advanced, empire loses against any large necron threat
chaos: cant seem to root out the imperium, but given this is very warp based, its hard to compare, chaos presumably wins since nothing star wars is based around fighting psychic shit
orks: annihilated by the empire