Good comments.

At least, my experience on MB and BMW told me that your comments make sense. I never drove Audi and Infinity before. But I think Cadillac is very unreliable. One of my friends got one, and he told me that it has too many small problems even in the warranty period.
I would rate BMW as the number one luxury car. Its handling and performance is unbeatable. After you drive BMW, you will not like others.