My opinion:

The 210 is a great driving car for the money, but I have no love for the '97 n/a diesel, it's a slug. If you're going to look at 210 diesels look at the peppier '98-'99 turbo, it is quick enough to keep up with traffic, pass reasonably quickly, and can also be fairly easily modified for more power. If you don't go turbo, get the E320 as others have said, a robust and fairly economical engine with good power.

Rust is an issue, cosmetically and structurally on these cars. It also exists on the late 124s more cosmetically, most common around wheel openings and body-clip holes (similar to W210s).

Which brings me to the 124. I've had both, and will take a 603-powered 124 over anything except a very clean southern '98-'99 E300 Turbodiesel. The 603 turbo is a great engine, a bit lower on power than the 606 turbo but I've never had a head issue and have run a couple of the #14 heads to 250k miles. Don't overheat it and be sure you keep proper fluids in the car, ... The later OM602 124s are also very good cars, but the power is IMO a bit less than it needs for the weight, performance more like the '97 n/a E300. Beware of the '90s wire harness issues in Mercedes cars.

I would rather have a diesel than a gas engine in my hobby cars, but feel that the M104 in the E320s is an excellent alternative otherwise. Drive one. In the 124 ('94/'95) it is very peppy, will smoke the tires with traction control off, same in the 210s. Of course this puts you in the rusty years and bad wire harness years with both cars, but if it is in good shape they are both solid and responsive cars with much more refinement than the earlier body cars.

I also agree with the other above posters, if you budget allows a W211, another level up in refinement and good quality. Each step increases purchase and maintenance costs, but returns a better car.

Start with your budget and decide, and remember the old saying that there's nothing inexpensive about a cheap Mercedes (et al). Give strong preference to an older car with good/great maintenance and a known history over a later car with a checkered past.

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Gone to the dark side

- Jeff