To begin with you are comparing apples to oranges.

Completely different platforms. The W123 is more of a "refined" model. Many of the /8's "flaws/quirks" were engineered out. Especially so in the case of your '72.

The 220D model was considered the "entry" level Benz. Not a whole lot of time was spent on making it a "luxury" vehicle. Those efforts were spent on the W108's, W109's and the W116's.

The W123 incorporated some of the design features of the W116 into what was more of an "executive" class car. More luxury features, improved ride, noise abatement, etc.

10 years and 100K more miles certainly have a lot to do with it also. The 220D was considered a "taxi" class vehicle and was designed more for its durability. Being used as a parts runner probably didn't help.

I prefer driving my /8 but for a drive of much distance, I'll take the W123 .

That changes if the drive consists of a lot of the "twisties" though. The /8 beats the W123 hands-down for sheer enjoyment.

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