2 cylinder engines fire 180 degrees apart, 3 cyl fire 120* apart. 3 cyl runs with less vibration, and is a slight bit easier to start, especially when cold.
Supposedly a 3 cyl has a smoother power curve.
All that said, my 2 cylinder puke green 240D will be celebrating it's 22nd birthday this year, and other than that nasty little incident of taking the teeth out of a final drive gear when it was 13 months old has only cost me 1 starter solonoid, and a few filters plus grease, oil and fuel in all those years. It is a cold blooded SOB to start in winter though, and always was.