Thanks so much KKK, jearund, and Corierra,
It's really helpful I think to know we're not alone here, this is a tough choice, but equally that we can't go too far wrong.
On the

side, Son is absolutely determined to put Pates as 1 even though we keep drumming into him (crushingly) that it won't work out - he's in the '+200 but QS' club & to make matters worse he is invited to Pates next week along with all that have or are likely to get in...not helpful, but he is determined not to miss it!
On the

side, all the views about STR and Crypt ring true, it's a great choice to have and we need to remember that and drum that truth into him too.
I think as things stand HE is leaning to STR, on the grounds of academic track record and the perception (rightly or wrongly) that it's stronger on the grounds it has taken the higher rankings in the past. I'm mildly favouring Crypt, and he knows it, (and we are going for a more intimate / 'normal school day' revisit next week), so it could come down to 'who decides?' - i suspect it will be him
In that case, my only worry is the burden of the decision on him - so our job as parents is mainly now I think to do everything we can to make it an exciting really positive choice and not a stressful one - they didn't teach that at NCT!!!
i'll definitely update & keen to hear any more views