I think the part that's constantly fascinating about the Tesla cars is that these features are being delivered as software updates. This would be like a software update that switched your phone from 3G to 4G.
Although I agree it's a cool way of rolling out features it's more like buying a phone with 4G capabilities but it not being rolled out until a software update; It's always been possible in the cars they just got the federal approvement now.
In one sense, yes—though I would also compare it to some of the cool hacks NASA does getting orbiting telescopes and Mars rovers doing new things they weren't doing before. All the sensors and motors and antennae are there, but a firmware update can put them together in new ways to enable entirely new high-level behaviors that weren't being considered or planned for at launch.
An example in this vein: imagine a firmware update to a wi-fi router to give it MIMO support. A MIMO antenna isn't any different than a regular antenna; the difference comes in the baseband firmware doing clever-er math to pull out overlapped signals, spacially model their sources, and modulate its own output so the signal will constructively interfere for best performance at the destination.
In a Cliffs-notes sense, both vehicles seem to offer an autonomous driving mode in normal conditions. Like any other competitors, they both have a few unique features that are neat but don't really change the overall experience exponentially.
To be clear, I own neither a Tesla or a Mercedes currently and I'm basing this just on looking over the specs, but they appear to be fundamentally comparable.
