As you know my ds is in year 7 at swbgs. My dd is currently year 5, we are catchment for Kendrick and live in Bucks but she will only take Bucks and will hopefully join ds.
From my experience there is no pressure on the children to be sporty - some are some aren't. For the girls Hockey and Netball (and from yr 9 ish rowing) are popular extra curricular activities but as many don't do them as do! There is an annual interhouse cross country which is compulsory but that is fun as much as competitive. I've never thought of SWBGS as sporty (indeed I know many people who've decided against it as they feel it's too arty and not sporty enough).
This term there is an interhouse dance competition - this is compulsory but again it's a fun event.
If you look in (I think) the parent section on the website there is a list of all the extra curricular stuff - believe me there is something for everyone! Academically they have very high expectations and the children are expected to have a high amount of "self startedness" (sorry I'm tired and can't think of better words
) in their approach to their work. The work is marked very regularly (I'm really impressed by this) and is graded - substandard work or behaviour is not tolerated - I know of quite a lot of detentions which have been handed out. DS finds it a very friendly place, I think the children are immensely proud of their school and as such are quite protective of fellow Borlasians.
The major differences between the two schools are, imvho that Kendrick is obviously single sex and also that SWBGS is a much less diverse student (this is IMO the only downside to SWBGS) body - the students are, in general from within 6 miles of the school gate - Kendrick would give you a much more diverse cohort. They're also in two very different towns which again will have their pro's and con's in the 6th form they're allowed out at long break - where would your dd rather hang out? (Hanging out in Marlow is a major attraction for my ds!)
I would go for SWBGS but then I'm biased
Drop me a pm if you'd like more specific info re SWBGS.
eta the traffic in and around Reading is dire!! The Marlow Donkey train service seems reliable and Marlow traffic as much as I've moaned about it over the years is waaaaaay better then Reading!