I agree that it's a matter of personal preference.
I see the C280 as a 7/8 version of the E320.
Their performance is probably very similar, and I wouldn't expect really any noticeable difference in handling.
The E320 is a little wider so you'll have more elbow room, and about an inch more legroom upfront, but the biggest difference will be in the rear legroom.
Most people rarely, if ever, have people in the back seat, so this might not be important to you.
Both cars unfortunately will probably need to have the head gasket and wiring harnesses replaced as the early designs were bad, but other that these two things, the cars will probably last longer than you'd be willing to keep them.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".