I would do some checking:
1) If it has been serviced continuously at a dealer, the records will be available. Ask to see the MB record print out on the car.
2) Search the archives for all the 'issues' on this model, and verify if they have been done.
3) Ask to take the car to your tech for a PPI - one that involves an overnight with a cold start in the AM.
4) Ask for an EXTENDED test drive - all day and overnight, like you used to be able to do with cars in the early 60's.
If they won't work with you on the items that need repair, or discount the price, or throw in a 25-50 k extended service contract, or let your tech inspect it, then I would walk away. Ditto on the BMW - I would personally rank 76k BMW miles with 100k MB miles, and you still have to research the BMW 'issues', service, etc.
Good luck on the search, and remember, if you find one as perfect and documented as you and I would each demand, it is probably going to be a premium price, as someone who maintains their car that well knows what they have, and also knows what they will have to spend to replace it with something comparable.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E