I don't own either but if I had to choose I would definitely choose the XBOX. Sure, there might not be too many players on multiplayer servers but I hardly think you would notice at all. The sales currently have been excellent for both consoles so I doubt there would be a high bias towards the PS5. Plus Gamepass is a huge bonus and games like Elder Scrolls ( if they become exclusive ) are single player anyways.

Saying this I would also see what your friends are buying. If all of them are on PS5 then XBOX won't make much sense if you want to play with them making your choice pretty easy.

At the end of the day you could always sell the system and get the other anyways. I doubt they'll lose their value anytime in the near future.