I'm very new here, but I am in the process of buying my son his first deer rifle and I put up a post like this (in the Gun forum down below) and found the same back and forth between about 4 or so different caliber's with all very good arguments for why i should pick one over the other and came to a really good way to decide on which one.

I am taking my son to a indoor rifle range (tomorrow after work) at one of our city's gun shops were you can rent guns for like 9$ + ammo and just let him shoot some rounds through them to find what he likes best

Get a list of 5 or so caliber's from the pro's here and let him sample each one and the one that he likes best is the one you go with. Every major city has an indoor range with gun rentals don't they?