Quentin- I have not been able to shoot any of his ar's so you could be right. I can only speak to the passion of the man when talking to him about his products and the fit and finish of the handguns I have seen while in his shop.
Now everyone I know says BCM makes "the best" BCG's. People say they are the "only way to go" and that if a BCG is not MPI'ed and HP tested it is potentially gonna fail. I think some of this is valid and some is not, MPI can find surface fractures but does not find internal problems. I'm not sure of the process for HP testing, I'm sure someone here knows the ins and outs of it and what it finds.
All in all I think BCM is probably the way to go when you can get them. Personally, I think that BCM offers the best quality vs. price and I would have a hard time spending more on a potentially inferior product.
That being said I'm perfectly happy with my stock RRA BCG