Stick with an escort, there really are only two radar detectors to buy, and thats the escort or the valentine 1. Both have different features and they are about the same as far as performance goes but any other radar detector is a waste of money.
And Blake is right about your dealership, they just want your money, bottom line. I would find a independent shop to install the escort for you if the dealer wont. There is no way that a radar detector can void any warranty or cause any issues with your vehicle, I would call BMW NA if your dealership keeps feeding your misinformation and garbage.
LeMans 135i ///M-sport 6MT