Looking to get an Audi A6, Mercedes E-Class, or a BMW 5 Series... so which one?

[RobertHaphazard]

For my 18th birthday my dad said that I could choose a car (reasonably), and I was looking at these three cars. I really like the styling of all of them, as well the prestige that comes with the brand names. But, admittedly, the Mercedes and the BMW just look a little grandfatherly to me. Which do you think is the best car (styling and quality), and not only that, the best car for an 18 year-old.

I would appreciate answers from those with personal experience in the car business, namely those who own these specific cars. Please do not answer if you just like living and driving vicariously through others.

Thanks for all the help!