Id go with RMP.
I used to go to Bimmersport back in 05/06 but I stopped going there a few years back...Charlie rarely works on the cars himself anymore or monitors whats going on. Jon is a nice guy and so are most of the techs, but I trusted only Charlie with my ride and once it became clear he was not touching the cars anymore, I went to RMP.
Rocco spends a lot more time on the cars in his shop himself, compared to Bimmersport, and plus you can never beat the service you get at RMP.
Always 100% professional and they dont play favorites (i.e if you're a buddy of one of the tecs at Bimmersport, they mysteriously find a way to fit you in right away, otherwise you better wait a few days and also end up leaving your car with them all day. Oh and the $ quoted also goes down ! I've witnessed that several times!)
At RMP - I've never been pushed aside for anyones 'buddies' - service is fair and no favoritism. Price is standard for everyone.
Thats all one can hope to expect. So RMP for the win !