Without knowing what models of those cars we are discussing it's hard to make a meaningful contribution here. As I noted, the offerings run the gamut depending on the series/class. Just because it says BMW on the bonnet doesn't mean it's a luxury-esque variant, it could have been a 320i or something, same with the Benz.
7-series review here:
If you're into large, luxurious sedans or you're lucky enough to have your own chauffeur, the 2021 BMW 7-series is a handsome and comfortable choice.
www.caranddriver.com
Some pics:
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The 7-series (and the more upscale 5-series offerings) are incredibly luxurious, not just in terms of appointments, but also ride, comfort, silence...etc.
Even my sister's 330i "Performance" pales in comparison in terms of the above to my similar vintage M5. I've also had a few rental MB C-class cars and if that was my benchmark on MB, I would be of the same view as you. You have to experience an E or S-class to get a proper frame of reference.
But, keep in mind, you pay for that. Even the base entry into the 7-series, the 740i, is roughly $90,000USD. The 760i is $160K.