From personal experience, I'd avoid the W210 wagons like the plague.

Partial list from ex-wife's 2001 E320 (no 4matic):

1) Trashed harmonic balancer
2) Constant electronic issues ranging from dead COMAND components to disappearing dash displays
3) Head unit (combo stereo/nav) replaced 4 times under warranty
4) Dead window motors (both rear doors)
5) Dead seat motor (driver's)
6) Dead transmission controller (x2)

Not experienced but known of: failed spring perches (often well hidden by undercoating until catastrophic failure occurs).

__________________
1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man - given away
1980 Redhead: Darling Wife