Steam. Premium Edition already bought and pre-downloaded.
Wanted it for PC for 60 fps at 1440p but don't trust the Microsoft Store or Xbox app to not mess up a 120 GB install based on previous experiences with their games. Steam also has options to verify and move games much easier than the Store, which more often breaks in my experience, throwing up those annoying cryptic error codes, e.g. 0x800210ef. The Microsoft Store and Xbox app on PC, are at best, average and at worse utterly atrocious when it breaks yet another game with a patch and requires you to redownload the entire game. There is a good reason why PC gamers loathe the Microsoft Store and Xbox app, even Digital Foundry have made jokes about it.
P.S. Will also be downloading it for my Xbox Series X at launch as well on GamePass so I can share the save game and play it on a 55" OLED TV with surround sound and HDR. PC will be where I spend the majority of time playing the game though as I am not sure, just for the higher framerate which I feel is more important for a game I will be playing mostly in first-person.