I think you are comparing apples and oranges here. I can list advantages and disadvantages on all those for both engines and make you believe that both are good but you will be right were you started.
just a short version
diesel is a good daily driver and around town, coz of its low end torque readily available in lower rpms and makes you feel like driving a bigger engined car.
Diesel engines are more durable but in Pak ppl have this misconcept that they are high maintainance they are not.
Diesel definitly gives better mileage then petrol, that is known as a fact world over, I do not have to proof anything here.
Diesel, think about it why do commercial vehicles prefer diesel and not petrol.
I can write an epic here on diesels but from the current point and being in Pak Diesel has more advantages then petrol engined vehicles.