I suspect it all depends on who deals with you at the time of your visit. I've dealt with the Service Departments at Grays and at Carstins. I found Grays OK, particularly so when dealing with a warranty matter. More recently, I was very positively impressed by Carstins because I could (a) tell the car had actually been serviced* and (b) was given information suggesting a good level of product knowledge. I would definitely use Carstins again.
*as in there was clearly fresh oil in the sump. Every time I have taken diesel cars to main dealers (Audi, Fiat) the sump oil has been as black as it was beforehand. I was told that diesel is like that, i.e., oil goes black immediately. Even if you only drive 5 miles before dipping the sump. So why is it that every time the same diesel cars get oil changes at independents... and on this occasion at Carstins.. the oil is visibly clearer, remaining so even after a hundred miles or so????
I was told that the Audi dealers suck the oil out from the top, and when an independent did an oilchange on my Panda they got oil everywhere. Sloppy yes, but at least I could see that there had been a drain out from the bottom (including the c**p at the bottom!).