The water-cooled diesel generators are often preferred when the power required exceeds 5 kW. These water-cooled diesel generators can be made much quieter with a silenced cabinet around it. And when the power is more than 5 kW, diesel is also more favorable from a price point of view than an aggregate that uses petrol as fuel.
Mitropower.com has the water-cooled diesel generators with a 1500 rpm engine and a 3000 rpm engine where the 1500 rpm engine runs smoother, has a longer life and is quieter. The advantages of a 3000 rpm motor is that the aggregate is lighter and more compact.