I know a little, but not much (I certainly would not call myself an expert on them)
I know more about BMWs than I do about Mercedes, mainly because I ownd a BMW a long time ago (during the time I owned it, I study everything I could about them) I generally know more about vehicles I have owned frequently or owned for some time.

Maybe I should buy a Mercedes and check back in with you guys in about two years, I should be a M-B expert by then ...