1st thought should be what do their friends have?
2nd should be do you only let them play kid-oriented or let them maybe play some teen stuff?
3rd is what are they interested in?
I own both, and I'd personally say xbox is better with gamepass and probably has a bit more games for kids. However PS has a big following with spiderman and ratchet and clank. If they want racing games or shooters then xbox is better. If they want action/adventure then PS5 is better.
Yeah I thought it was a "I'll rough you up a little to show that I'm ready and you'll let me through" moment and it was anything but that