It's important to know by what criteria one is referenceing when they say it is the best. Maybe they mean it has the highest top speed or is the quietest. When I think best, I'm thinking about reliability and durability.
If long term reliability is what you're looking for, I've seen some posts on this forum that lead me to believe that this is not the most durable Benz diesel ever built.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in