I got both in the end - figured i'd get them eventually, so why wait? - and mostly play the Series X w/Gamepass. It's almost cliched to say it these days, but Gamepass is a total game changer. The key point isn't the massive library of current games or the prospect of the first party stuff on the way - it's that your mates all have the same games. I couldn't convince 3 other ppl to buy Deep Rock Galactic. Probably wouldn't buy it myself. All decided to try it on a whim and it's the best damn co-op game in a while. Street of Rage 4. Always looked cool, but wasn't going to splash cash on it and play alone. I've now completed it twice with different people and it's some of the most fun i've had gaming fullstop. State of Decay 2 - same story. Amazing game, if a little buggy. So good, in fact, that no. 3 is now my most wanted game on any system. This is just a few games - there's been other surprises and no doubt a shed load more soon to arrive in our collective library. If there's one criticism it's that Gamepass is gaming crack. And the joypad isn't as good.
The PS5 I like a great deal btw. Demon's Souls is fantastic. But that's all i've played on it. Unless Sony combine PSNow with PS+ and add first party games day one, it will be relegated to occasional exclusives duty.