OM656D vs OM642

[such01]

Looking at purchasing a W222 with either the new flat 6 OM656 or tried and trusted OM624 engines. I've seen some 18 plate "high" mileage 100k+ OM656's for sale and wonder if these will be a good buy vs 17 plate OM642 with 70k on the clock.
Are there any issues with the newer engines compared to the old V6? What can I expect maintenance -wise with ongoing mileage over normal servicing?
Are oil cooler seals still an issue on the OM642's from 2016 onwards?
Anything else I should be looking out for on a 7 year old W222?

Thanks

 

[toteimerced]

All I can say is, all the 642 faults are well known, with effective remedies, with documented 70k, it should be good, I would have thought, the oil seals were altered to purple ones, from 2010 on I think it was, so that shouldn’t be a problem, either way, it seems the biggest problem with most Merc diesel’s, is the terrible AdBlue systems.