It was one of the biggest topics of discussion earlier during this generation; is it better to have a battery built into your controller, or is it better having regular exchangable ones. Sony went with the former, which means you can just charge your controllers (which also tends to be more space efficient), but on the other hand, you have to play tethered to the console while charging unless you buy more controllers (and the batteries won't be as good after a while).
Microsoft went with regular batteries for the Xbox One controller instead. It does make them chunkier and you need to have batteries (or rechargeables) at home, but you will be able to use your controller after switching batteries, and you will never have to replace a controller because of a bad battery.
There are pros and cons to both approaches.
Sony is expected to continue with its approach for the PS5 - and Microsoft has already confirmed that it'll stick with batteries. And now Jason Ronald from the Xbox team has explained why to Digital Foundry, saying that it's roughly 50/50 amongst gamers on which battery solution they prefer:
"What it comes down to is when actually talking to gamers, it's kind of polarising and there is a strong camp that really want AAs. So just giving flexibility is the way to please both [sets of] people... You can use a rechargeable battery pack and it works just like it does on the Elite, [but] it is a separate thing."
Xbox Series X launches later this holiday. You won't have to buy new controllers from the start as the console is actually backwards compatible with those from Xbox One - but batteries you will need regaredless.