I'm in a weird situation. I'm definitely more invested in the Xbox ecosystem and would want to get a Series X before a PS5 theoretically (even if I'm going to end up owning both in a year or so), what with having Game Pass for two years and not needing then to buy any game at launch (maybe something third party, dunno).
But at the moment I own a Xbox One X which is serving me pretty fine and a base PS4: most first party games are going to cross-gen so I'm legitimately inching towards PS5 for starters, keeping my One X to play Halo and the rest of the stuff, even if the launch line-up of PS so far hasn't done a lot for me (except for Deathloop). I will though wait to see release dates, prices and how big of a difference there's going to be in titles such as Infinite (my priority for this year) between One X and Series X before deciding. If the games will run without too many compromises on the One X, I'll keep it for another year and start my next-gen with PS5, where I also have to play some stuff like God of War and Spider-Man that I left behind.