W210 is DIY friendly, and a lot more electronic than the 80's era W124 design.
The W211 has electric assist brakes on pre-facelift models, which makes brake pad changes dangerous if not diasarmed first. I think you'll find, based on my experience with the W210:
it needs a lot less maintenance than the W124 and similar
the maintenance jobs are DIYable
some maintenance jobs may require some extra tools (eg tranny dipstick) and cost more (eg tranny fluid), but given that teh jobs are less frequent, you cpome out about the same
it's mostly plug and play. No adjustments needed. If something breaks, use the codes to diagnose and then replace it.

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Prost!