even though I don't own either one, but a diesel w210, I'd say go for the E55if you want to play with it on the weekends and take on occasional drive out and about. From reading other posts it appears to be much more of a comfortable car than the 500E. The 500E appears to be a collectors car. A highly engineered vehicle that has one purpose, haul ass!

As far as performance of the E55, there are aftermarket parts to really make the car perform, upgraded springs, shocks, swaybars, etc.... I have found the w210 a nice car to work on. Either way they are both some fine automobiles.... PLUS, it'll be MUCH easier to find an E55 in better condition and less mileage than a 500E...

Check them both out and see how you like the feel of each. If you're tall, I bet the w210 cahssis may feel more "fitting" for a tall frame.