Diesel and Petrol engines are very different from eath other, as one is aware they are different types of fuel.
A petrol engine creates combustion via taking in petrol and air, compresses it and then igniting it with a electrical spark.
A diesel engine creates combustion via taking in air, compresses it, then is diesel is injected on to the hot air, creating a ignition.
Petrols mostly run compression around 12:1 while Diesels run compression almost 22:1
A higher compression means higer torque at lower RPM, while a low compression is produces lesser torque at lower RPM. Petrol has a early detonation while diesel has late detonation, so this means you can have more pressure at detonation. A typical example is that if you pop a petrol in high gear it starts knocking, that happens when the pressure created cannot create enough momentum to produce enough torque to accelerate, so the pressure starts skimming through edges of the piston rings.
I am not implying Petrols are not good for 4x4, but rather explaining the differences.
A Petrol has higher torque at higher RPM, therefore, a petrol engine mostly built to handle RPM around 6000, while diesels are nearly as high as 4000 max.
A brief summary,
A Petrol can accelerate very qucikly but it cannot handle loads.
A Diesel is basically a donk, you can tow and put a lot of weight on it and it will carry on. I've got a diesel and when i put it in Low Range, i just have to pop in the first and leave there, don't even have to press the accelerator to get it climbing a ridge, but with a petrol you must have to have your foot on the accelerator.
If a diesel has to climb a hill, no problem, but it has t go slowly, but if you it hit with a petrol at high RPM, you will be on top before the diesel knows you even passed him. Remeber Diesel is Muscle, Petrol is Martial Arts.B-)