Mercedes interior materials and general quality isn't quite up to par with BMW (except for the S-Class), and I say this as a current Merc owner, but honestly they're all still very nice cars. My G30 5er had better interior materials and quality, yet I still prefer the more interesting and modern design of my CLS (but in the end looks are subjective), and the inferior materials/quality didn't sway my decision in going with the Mercedes over the BMW at all as I greatly enjoy other aspects of the Merc more.
I do agree that they messed up on the GLE/GLS interior though. There's a lot more hard plastics in the GLE that a similar spec'd E-class doesn't have (For example, GLE gets hard plastic lower door pockets but E get soft touch even in base form
) despite the GLE being labeled by Mercedes as "The E-Class of SUV's." I honestly think BMW just hit a home run with the current X5/6/7 interiors. They took the great quality and materials from the 5er and 7er, but fixed the boring design they both have and modernized it.