I’ve worked in two boarding schools, and I would definitely say go what fits with your kid. If they want to have access to academic staff, libraries and extension activities like star gazing, do eight hours of sport a week, DofE, CCF, music, drama etc then a six day a week, either as a boarder or day pupil is super fun. If the school doesn’t fit for you, it’s pretty hideous. Most of the boarders at the school I’m at now live within 30 miles of school which means they see parents pretty often. I think you get a forces allowance for boarding (regardless of school) which would gives you lots of options (depending on where you live).