Hey, I'm the anonymous European poster!
I've posted some PM concerning this question to members who own both series but now there's a thread (thanks vstech) so I'll tell more about my quest here!

So I was looking for a w201 or w124 Mercedes diesel that I'll use (here in Europe) both as a daily driver and as a long distance cruiser (I mean 5.000 - 10.000 km trip in Eastern and Southern Europe where roads are not always highways...). We got a good bunch of roundabouts, speed bumps and mountain roads but I maybe emphasize a bit too much those negative points.
If it can help, I'm 5'9" and often travel alone or with a single passenger (but obviously it's always a bonus to have usable rear seats...)

I've decided to narrow my search to NA diesel only with manual box, performance is not a relevant parameter, in order to maximize the reliability and reparability of the car. A w124 300D or w201 2.5D would be perfect but I can't decide which type I should preferably get. Our 300D come with the OM603 but contrary to the US version sold in 1987 we had no EGR or trap oxidizer in France until 1993 and the new OM606, add to that the fact there's really few turbo versions, this engine has never been considered as a dog due to poor headgasket here.

The real hesitation I had was about the comparative size of w201 and w124 and the build quality of those 2 models. I've read that the w201 was truly made as a premium car but some users complain about poor door panels or wood paneling, I've also read that sound proofing was not as perfect as in a w124.
On the other hand, I'm a bit afraid by the larger weight and size of the w124, plus there's maybe more electric equipment inside that might be harder to repair.

I'll read all your advises but it already seems clear that, although the w201 is perfectly made, the slight bigger size of the w124 is quickly forgiven as it's better on almost every levels.

And yes... money is not a problem as w201 and w124 are still widely available in manual transmission here. And as I wrote to a poster, you can right now even find almost ten 190D 2.5 turbo manual for sale on various French websites for less than 4000$

Kind regards to you all

TLTR : I hesitate between a w201 and w124 NA diesel manual for trips and daily driving in Europe.