Advantages:
Diesels are noisier and need a longer time to warm up in the morning. This may sound like a disadvantage until, at 530 in the morning when you are leaving for work, you remember how ANNOYED you were with the next door neighbour for idling his power boat in the driveway when you were trying to have a nap. THEN it seems like a lovely advantage. :p
Diesel pumps may be fewer and far between, but there is almost never anyone AT the pump, so you never have to wait.
YOur hearing doesn't have to be as good as the dog's to know when your spouse just pulled in.
Diesel is far less flammable than gas, hence a safer vehicle.
Diesel is also and excellent engine cleaner (if you've ever had an injector line come off you know what I mean).:p
No spark plugs to buy.
The best advantage to owning a diesel... visiting this board!
Disadvantages:
Not too many to choose from (compared to gas). Much more limited production.