I enjoy my SDL for it's longer wheel base when I have family around, no packing into one of my smaller vehicles anymore. The motor is more powerful too (obviously). But the noise the 617 makes is great.
I wish MB had threw an extra cylinder on the 617 (it'd be a 3.6L then) with an aluminum head instead of revamping the block too. No rod bending, more torque, and more HP.