Overall impression: the E450 feels more solid (it's 400 pounds heavier), and the G70 feels more agile. I didn't order Head-Up Display for the E450 (it was available), so that's a nice upgrade on my Prestige model. And the safety warnings are much more aggressive on the G70 (I didn't get all of those options on the Merc); very much appreciated now. Also, Digital Key 2 wasn't available on the E450. Probably the biggest single difference is not with the cars, but with the companies. You can tell that MB is operating with a 129-year head start over Genesis.
P.S. The Merc has (at least) a couple of extra tricks:
1. Its headlamps swivel left-right and, when you turn, the Merc will swivel them to illuminate the road
where you're going, even though you aren't pointed there yet.
2. The Merc has optional support for
dashcam, which captures the forward-looking camera to a user-supplied USB stick.