I could not agree more with Lucky.
The W124 beats the W210 in all departments other than gas mileage.
I have been playing with the thought of getting a W210 for years, but whenever I test drive one I go: Nah, the 400E is a lot better, so I just had it upgraded to 94-95 looks and am now flirting with a 94 E500. Now the 400E looks timeless and in my opinion beats the W210 in looks hands down. I also agree about the statements made about the quality of interior components and the overall quality as well. The W124 feels solid whatever you do to it and looks expensive and quality inside and out. No plasticy look here. No dissapointments here.These are the last E-Class build to meet a standard rather than a price.
In regards to the BMW comparison, it really is a matter of choice for the average consumer. If you're a DIY'er the Benzes are a lot easier to work on and as preveiously stated cheaper in parts, even the V8's. Personally I would not go with a BMW as it does not really give you the 'King of teh Road" feel the way a Mercedes does. Then again a matter of personal preference as they are still very nice cars.
Good luck!

__________________
F.J.
81 300 SD grey/palomino 168K miles
84 190E 2.3 black/grey 64K miles (wrecked)
85 190E 2.3 maroon/palomino 92K miles
88 300E desert red/palomino 204k miles
(made to look like a '94-95)
92 400E desert taupe/creme beige 120K miles
(converted to 94-95 E420 looks)