I have a customer that has several Freightliners with the Mercedes engines that I do sevice work on, they have between 100,000-200,000 miles on them with few major repairs. I've worked on all types of big trucks with all types of engines and would not have a problem with buying one with the Mercedes engine. With that said it also depends on what the intended purpose of the truck would be.
Also doing a filter change on the Mercedes is very easy