We made the same choice - except we moved to East Dunbartonshire for the schools rather than East Ren.
No it's not the same as private, but the state secondaries in Bearsden and Milngavie are pretty much the best you can get in the state sector. Brand new school buildings with good facilities, good head teachers, good teachers, on the whole.
Yes parents in our area are pushy and want their kids to achieve, and will question school decisions and challenge them. Especially over the last year. Yes some kids have tutors (my DD had one for maths) but not all by a long chalk. School put on extra revision sessions during the Easter holidays or after school to support kids who are struggling - and in my direct experience they are prioritising the kids who are hovering around the 50% mark and could go either way to push them into a solid pass rather than hot housing the able pupils to guarantee an A band 1 pass.
Loads of extra curricular stuff like debating, sport, D of E, drama. Active PTA and Parent Council.
Schools are full but once they're full that's it - no placing requests. Catchment children still get a place.
It all depends on your preferences. Personally we felt that choosing to move meant that we were investing in an asset (the house) which isn't going to lose value. The extra money we had to spend to live here is less than the costs of sending 3 kids private. More importantly though, it was about them having a good set of friends locally, within walking or cycling distance. I do have friends who send their kids private and their friends live all over the city, so they're constantly driving them all over the place.
Ultimately though each choice is equally valid and you have to make the decision based on your preferences and what works for your family.