We have all three: Switch, XBox One, and the 11yr old boy
My son prefers the switch over XBox but the XBox is better for when playing with friends. XBox with Gold sub is the best value and I don't buy games as there are enough titles in our library from the games with gold.
Switch service is a dissapointment but needed for online play. Cheaper but as mentioned titles are more expensive. My son plays mostly Zelda, Splatoon2 and Fortnite.
I as a parent prefer the switch due to the parental control app on my phone. I can lock / unlock his device and allocate his play time. I can also monitor what he does. Used it the other day to get him to help me fetch stuff from the car. I did not feel like shouting his name so I just disabled his switch from my phone, 10 seconds later he was running around looking for me
To be honest get both.