A touch screen screen is worse than a control interface like i-Drive. It's alomst impossible to drive and touch the screen in the correct place on UK roads.
On your Mercedes E Class and BMW 5 Series comparison - you're comparing a 7 year old 5 Series design to the latest release from Mercedes; so probably not a fair comparison
For contrast, here is the Mercedes equivalent to the F10 5 Series. This is a 2015 car I rented last year...
It was like being in a time warp