Well, my experiences which are obviously out of date and personal were that your dd's school is very academically based, and I didn't feel that it helped you develop as an individual. Having said that, the teaching there is excellent, but looking back I wonder if there was too much emphasis on results rather than happiness. If you want to CAT me I can give you a few more thoughts that I don't want to put on here!
DS - well, it is a totally different school - because it is a boarding and day school, the day is longer, so there is more time for extra things. There is a big emphasis on sport, and a huge number of sports on offer, there are lots of different musical opportunities - just about whatever you're interested, lots of drama etc. It is different to your dd's school I think because of the house system - they are physical houses, so there are smaller communities within the bigger school community, and lots of things happen as part of the house system. This also gives the benefit of both single sex and mixed education - the houses are single sex but the classes are mixed for lots of things.
The current head is retiring at the end of this year, but he has moved the school to being more academic than it was (though it is still not particularly selective). It wasn't as focussed on academia when I was there, but I still managed to get 5 good A Levels (I did Music, Maths, Physics, Chemistry, Gen Studies and got AACBA in that order, so was absolutely fine). But I think that is a bit more important now! Again CAT me and I can give you a few more thoughts.
I don't know much about the Newcastle schools - my cousins went to RGS and Central High, and my dad went to RGS, but that is obviously a while ago, and was before it was mixed.