'02 would be 'face-lift' model of W210. As mentioned different front bumper also nav system, controls on steering wheel, side air bags in back when compared to '99. Depending on where you live a 4Matic might be preferable.

AFAIK, both used the 722.6 5 speed electronic transmission. 722.9 7 speed was first offered with the '03 W211

IMHO, when it comes to purchasing an used car it's all about it's condition, level of maintenance and asking price. Which car was best when they were new is pretty much irrelevant now.

Service records with no gaps are a plus. Lack of them is a red flag. As a previous MB owner I'm sure you know about the brand but almost everyone is better off getting a pre-purchase inspection from a qualified MB mechanic.

Good luck.