SAPS level, HTHS, TBN...and experience from users, some have done UOA, etc.
Mobil Delvac 1 5W40 is probably better suited to be used in a diesel engine in harsh condition (does your engine has EGR?), others are primarily designed to light duty diesel.
There's not much I can add, the mobil Delvac is perfectly suited to your engine, so unless you want something thinner for the winter or are experiencing some issue, you can stick with it. If you want to try something thinner, then the other oils on your list are perfect too, there's no "bad" oil in your list.
Edit: should I be able to buy Mobil Delvac 1 5W40, that's what I'd use in my diesel. And M1 0W40 in gasoline engines.