You're missing a lot.
They've been battling each other for decades. Always trying to come up with something new.
The biggest differences are under the hood. Hidden from the naked eye. But a true car fanatic knows that both companies have a different approach.
Mercedes is generally speaking better though, because they've simply been faster and more sturdy in the last 15 years. Plus they have a better variety of models. Always had.
With Mercedes you just know that you're getting something good and new.