John F is consistently anti-MB based on a handful of anecdotes. Here's mine: during my first 12years of car-ownership I ran 3 cars from VAG whilst my dad had 3 E-Class's of varying models. In that time I had 2 stuffed turbo's, a broken final drive on the gearbox, split hoses on the turbo system, a leaking brake servo, various electrical niggles and one big electronic issue the airbag control module due to VAG inability to properly seal their cars from water ingress. The more reliable VAG car was my Passat 2003 estate but a crash wrote it off as VW OE parts were stupidly expensive. I also had rust issues on my A3 3 times which were a battle to get fixed even though the car had full Audi history - granted my dad's 2002 E Class also had rust issues but MB fixed that under goodwill even without full MB history. So after the Passat I made the logical step to an MB C Class and am now on my 3rd.

Mercedes can be expensive to own/maintain but that's often IME down to lazy servicing and cutting costs by owners. With a service plan and a recent 20% discount from MB my C43 AMG is as cheap/cheaper than Audi servicing. The key thing is look around for an MB with full history either from an MB dealer or a good MB independent. If you're looking at an E Class around 3years old then it would be the first of the W213 model (which has had a recent facelift). The latest diesel engines (OM654) are proving reliable, as are the 9 speed auto-gearboxes. The only thing the head-tech at the local MB (also a close-friend) tells me is that MB history is essential as there's been quite a few software updates due to the various tech now packed in to the cars.