Yes, I had similar thoughts, am in catchment for RLS but my son and I were very impressed by AGS. However, we really liked RLS as well and finally settled on putting it at the top of our form - mainly because of the journey which sounds a weak reason but....we live in a small village and in normal time the journey to Aylesbury would be ok-ish, an early start, a car ride to the bus stop and on the journey back a similar scenario. However, if the boys then decide to partake in sports or after school clubs they could in all probability miss the later school bus and the local Arriva (or similar) bus only runs once near to our village during the late afternoon, so it would mean us having to trundle into Aylesbury in the rush hour to pick him up.
We then did a dummy run and the return journey on this particular evening return took 80 mins. Fine, every once in a while but one of the boys showing us around who also lived in a village near us said he regularly missed his transport and sat in the school library doing homework til 6.30 waiting for his parents lift and said it was the down side of living a long way away.
I have older step kids and my husband has been there and done it all before, he says the worse situation was when his first batch of kids did not go to the catchment school but to a school a distance away and then found friends the same distance again away from the school in other direction so weekends, holidays etc. were spent dropping them off miles away - I suppose we could insist on them only finding friends with certain local post codes to save on our time and petrol!!(hahaha)
I must admit I am not really considering A levels as that seems a long way off and a lot could happen. My son has sisters and girl cousins so the girls v boys thing, if they went to an all boys school did not seem a problem. As I've already said, if the transport of children to AGS suddenly improved for us personally, it would have made the final decision harder.
I am sure there must be a few parents out there who actually have kids at RLS and wish they would have sent them to AGS and vice versa, so as you say, it will be interesting to hear what they have to say.