It's all dependant on the local dealer, in the same way it is with independant garages. There are good and bad with both.
I work in the motor trade, and have used one independant garage for most of my motoring life. Having bought an ex-demonstrator earlier in the year (the newest vehicle i have ever bought) I took the decision to have it dealer serviced.
We had a Seat a few years ago thinking VAG build quality, we were SO wrong! In 5 months we lost over £2000 when we finally got rid of it.
As this car is under a year old we thought that if that turned out to be a bad one, and had no dealer stamps in the book, this would put a LOT of people off.
As I say, i work in the trade so know all about block exemption, OE quality parts and so on, but the general public dont neccessarily.
Anyway, my dealer gave me a fixed price with trade discount, collected it and returned it. BUT, the main thing that my independant wouldnt have picked up were two little warranty issues. Nothing serious, just the ignition key receptacle is tight and one of the comfort features has a fault logged in the ECU.
Overall, I was very happy with the level of service I got from them. They know the specific model very well and do any software upgrades as required. The chances are that if for example they had said it needed brakes pads then I would have got them to price doing it, but most likely got my independant to fit some that I supply myself.
Horses for courses really. It depends on so many varying circumstances of what you own, what youre having done, and so on.