Funny, I just read that thread too! The poster had a point, but I'd say this is only one side of the reality in Salisbury
I grew up there, attended a grammar, moved to East London now hoping to return to be near family as I now have a child
Fwiw I don't remember feeling immense pressure at the grammar or to pass 11+ at my 'crammer' primary. (although my parents were pretty pragmatic about it which had an influence ((lefties, politically, they do exist in Salisbury!)) I also don't recognise this talk of 'hot housing' and found my education at the grammar encouraged me to think deeply and independently. So that's my 5p on Salisbury grammars
I'm now a teacher and the state secondaries in Salisbury have vastly improved in last few years. I'd happily send my bairn to wyvern/St Edmunds (which have a fab pastoral/sen team and is now co-ed, something I like)
The issue I think is the lack of stuff for teens, but I think most teenagers get bored with their neighbourhood in the end. I found it was the kick I needed to focus on school and get into a uni somewhere more interesting
I hope that returning will bring us more space, both in housing and the surrounding countryside, a more settled and calm pace of life i remember. I also think being a big fish in a small pond isn't so bad for a child, compared to the potential of drowning in the commotion of London or a larger city
Best of luck OP wherever you choose, but Salisbury would get my vote, especially as some great independent businesses have sprung up in last few years and the art scene seems to be getting better and better