I have a DS at WBGS and am impressed by Music, Maths, Classics.... just realised I am writing the same list as 3b1g
Seriously, it is a great school and we are delighted with it. As tense mentioned, the biggest difference is coed vs boys only.
I have moved my position from being in favour of coed to preferring single sex especially for boys. I am of the opinion that the shared teaching at a coed benefits girls who are normally earlier to mature leading to better performance for girls which in turn focuses the teaching styles further in their favour. At the boys school the approach to teaching tends to use examples and methods that enthuse and engage boys better leading to boys doing well in subjects they have not fared as well as in coed schools.
Now this is my feeling but has been backed by some studies that both DD and DS benefit from single sex schools and my experience has born this out.
That said both schools have outstanding performances and you will not go wrong with either.