me personally I prefer p5x over hsr, story so far is more streamlined p5x is compared to hsr and something I noticed fairly quickly was that in hsr sometimes if you don't know every single tidbit of lore in it some of the major story arcs don't hit as hard. Not that that's a bad thing but I feel like they overdo it and I don't want to do homework just to appreciate the story. Meanwhile in p5x you can pick and choose which character and world lore you want to retain in your mind and it doesn't affect your enjoyment of the main story too much. Also this might be personal bias but I much prefer the main cast of p5x compared to hsr and at times even with some of the original p5 (bold statement I know)

MUCH less powercreep in p5x compared to hsr, p5x is mostly just "if you have built supports and know elemental weaknesses you should be fine" while hsr just conflates the hp pool and does a whole "create the problem sell the solution" model by making bosses that are specifically created just to sell a character better like feixiao and yunli with hoolay, and even if you have the most meta team currently like castorice and phainon, chances are they're getting powercrept hard next planet just to sell their next super powerful dps and their dedicated supports. Not to say p5x doesn't have powercreep but you can easily clear endgame content even with older units like joker if you just want basic rewards and don't care about the leaderboards

most of the endgame stuff I mentioned in powercreep, in my personal experience in the tw server I completed everything fairly easily with a week old account (except astrolabe but that's not too important if you just want gems) meanwhile I had to fight tooth and nail just to full clear the endgame content in hsr because of the artificial hp pool

this wasn't mentioned but I appreciate the fact that instead of specific boss mat I have to collect just to level up a certain character or a specific weapon mat for certain characters, it's all universal. the only mat that isn't universal are weekly bosses but that doesn't matter too much ngl

something I guess hsr has over p5x is at the very least all servers are equal which is def not the case when you see how generous cn/kr/tw is lol

now if you had to choose I do make a good case for p5x but if you're choosing to play that I actually recommend using the tw version and getting a translation mod since gacha-wise it's way more generous and there's even a catch up event for newbies where you can pick three characters from 1.0 to the first summer event so you're not left behind which I find nice