So I've got a 72 240D and an 82 240D, both vehicles I would say in excellent mechanical shape.

The 82 (Automatic) has around 175k miles

The 72 (Stickshift) true millage is unknown, I would estimate 250K miles.

The W123 is a MUCH quieter and solid feeling car, and I'm trying to discern if the W115 is just perhaps worse for the ware or if W115s are just noisier.

To be clear, the W115 is louder in EVERY regard - wind noise, rear diff noise, cabin creaks & rattles (has a sunroof) and the motor is a good deal louder as well.

I know the history of the W123 and it was a single family owned vehicle for its entire life til I bought it. While it wasn't in tip top shape when I purchased it 3 years and 40k miles ago, it was all original.

The W115 is a little more of a wild card - started life as a 220D, engine swapped to a 240D, was in an accident at some point in its life I think, and was used as a parts runner for an MB shop in TX.

Thoughts?

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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Agreed!! I've noticed the W115 handles a bit better/has less body roll and is just more fun on curvy roads.

The 123 is so much more refined, everything from the suspension to the seats are better at absorbing vibrations and road imperfections.

Okay, makes me feel better. I was worried my little 220D was at the end of its life span - and I really love its charm and character.