I agree totally.
The bottom end of either motor has no end. I have a current customer with 650k on the bottom of his 91 420SEL.
We did a valve job at 380k due to upper rail failure (our first work for this customer who drives to us from Jacksonville - 85 miles). Unfortunately at the time we thought the car had 180k on it as the speedo had been changed (so we didn't change the lower rails). At 490k the lower right chain rail wore through and the chain went again. At 600k we put VG oil seals on it as it was using some oil (its never used a quart between 3k oil changes except as the seals wore). This customer drives 90k a year but takes very good care.
When we did the job at 490k the customer was skeptical that he could get another 100k out of the bottom end. He has gotten at least 160k more and still going strong. It had almost no cylinder ridge at the time it was last apart.
Bosch Master, ASE Master, L1
33 years MB technician