I upgraded The Shark to BRM this year, and I'm thinking of reverting to BR for next year, mainly so I can switch to instant validation and not have the hassle of post-processing all the brevet cards, labelling envelopes, etc. I've also had finishers right on the time limit, so feel that on a fairly challenging ride with a fair few first-timers, it's only right to give them as much time as possible to get round.
I agree the ACP stamp does add a touch of class, so I might just go BRM on alternate years (as I will have to for 2019) as a bit of variety...