W221 Bluetec vs W212 Bluetec reliability

[Überlandung Geländewagen]

Hey all,

Looking to retire my 240D to weekend duty since I have a long freeway commute to work now and am looking for a daily upgrade. I'd like to stick with diesels given their relative efficiency, and am currently looking into the W221 S350 Bluetec and W212 E250 Bluetec. How is the reliability between the two, and which one would be more reliable overall? Would love some input from owners. Thanks!