Which engine is better diesel or petrol?

Diesel - because the combustion is better, you get more energy per pint of fuel. But if you want more "Bang for the bucks", a petrol engine will give you a more rapid acceleration. The diesel engine has another property: it will operate well with a wider span of rpm: e.g. it can give you 75% efficiency at 2000rpm, and keep on going to almost 5000rpm. If you drive a car with a manual gear, you do not need to change gear so often. In a boat, you have to change propeller, which is cumbersome, but here the diesel has even a bigger benefit, since it will work good at slow speed - say 5 knots, and equally at 25 knots. Usage of turbocharged and advanced injection makes the modern diesel engines almost as fast as petrol, and what remains then is the sound. To get the same sound as a angry petrol engine. So, if you want to impress the girls, I would say that the petrol engine is better.