The trouble it is such an individual thing, from family to family, isn't it? What works for some people doesn't for others. What was your vibe first time around (when you looked at the schools for open days) Classicsgirl? DS really liked Sutton and Wilson's. He favoured Wilson's above Sutton but we felt the reverse! But then the DSs are the ones who have to go to the school and not us!
As I said unfortunately we don't really have very direct past years' experience of the schools through close familial or friends' links, so maybe not the best to advise except for our own impressions!
But I have heard many parents on other forums say that actually WCGS is excellent on pastoral care - just to throw a spanner into the works!
But it is all relative and probably depends as much on the character of one's child and possibly the Year 7 Head (which might change year on year?) too. I guess just because Wilson's is a larger school it might lack the relative intimacy of Wallington and Sutton....
Am interested by your response about your letter from Wilson's, Classicgirl. Was that your DS's first choice? It was our DS's. I found the letter about going on their waiting list to be very 'flat' and we couldn't really read twixt the lines and see whether it was or wasn't likely that DS might be offered a place at a future date. Sutton's on the other hand was highly encouraging, friendly and generally a lot more helpful. That may or may not say volumes about the general attitude/ethos of the respective schools. Or it may reflect how well or not DS did in his 11+ exams!
Have you both considered flagging up a direct question on the 11+ Forum? I seem to think that there is a similar question thread at the moment - or one that you might be able to feed into!