For me it all depends how long tou intend to keep the car. If you are going to change it next year, then go to the dealers and maintain your full vwsh. If you are keeping it another 3-4 years, then I'd go with whoever offers the best value for money. A folder full of receipts showing that the car has been looked after is worth more than a book of dealer stamps to a buyer of an older used car. Having said that, dealers labour rates reduce for cars over 5 years old, so it may be worth suffering a big bill now, knowing that the next one won't be as bad and you'll still have a book full of dealer stamps.