When buying a console, the only question that matters is what games you want to play on it.

Xbox One X is the last generation model, so it won't run newer Xbox Series exclusives. The line between console generations is quite blurry these days, the Series line has been out for over five years and some games still get cross-generation releases, but even then you should be aware that cross-gen titles may be poorly optimized for older hardware.

If you're only looking to play games from the Xbox One era (2013-2020), those should all run great on the One X and you can save a lot of money by deliberately staying a generation behind. See !patientgamers

But if you want to play anything newer, if you want to be future-proof going forward. Series X is the high-end current generation model for current generation games.