Strange league table results for RGS - if you looked at the Times it would be different... for my son's year they were 3rd in A level results... RGS is always stronger academically... If your son has been offered a scholarship he must be exceptional - so you'll want him to go to a school which can routinely deal with his abilities..
... but the only score that counts is your own son's, so its really down to where you think he'd do best.
RGS for music is fantastic - my son was a pianist and they are so strong they have not only a head of music but a head of keyboards. They have concerts just for pianists, as well as the usual range of symphony, jazz etc. They also share a chamber choir with GHS.
Others have commented on sport. but you might also want to think aobut their Art dept which I think is second to none - my daughter did some of her a level are classes there and she thought they were better than her own school. RGS art displays are always fanatastic.
You dont have to be sporty to love RGS - my sone never challenged the scorers, that's for sure.
I also like their "Monday 8" activities - a compulsory extra currciular choice of CCF, DofE or scouts, which stay on the timetable right throguh to 6th form.
I'm not trying to sell RGS against Hampton - I only know the one school - but highlight these as some areas which are outstanding