both are really great cars. My guess is that the 96 280E was a typo and you meant 86. 86 was the last production year for the 280E and 93 was for the 190E, so that's good.
I can only say from personal experience that you wont be disappointed with the 190E 2.6 as long as you keep up with the maintenance. The engine likes to eat gas pretty fast if you're a fast driver. So if gas cost is important to you, I would recommend the 2.3L version instead.
Between the two cars, I would pick the 190E even though it has higher mileage for the following reasons: newer car, engine has more power than the 280E, and I have owned one myself for 4 years and would definitely buy another one if a need ever comes up.
Also make sure you ask some questions regarding maintenance for the 190E, such as,
-when the head gasket was last replaced
-whether the water pump and water pump assembly is new
-when you test drive the car, listen for any transmission hesitation when going from 3rd to 4th gear.