I've only driven the sedan versions, and only for a test drive with a 124.

The 210 is a bit larger and drives like it. The rack and pinion steering is a welcome change. The additional electronics may not be.

I haven't seen any sign that the 210 evaporator is as unreliable as that in the 124 or 140, but this could be simply because they haven't been on the road as long. It's not like all 124's and 140's will need evaporators (not even close), but it is a fairly high failure part.

As for head gasket leaks, that's a function of the engine used and not the platform. The same engine in a 210 would suffer from the same maladies.

Given the choice (again), I'd still go for the 210.