Neither. I think that's perception more than reality. I've certainly not noticed any more reporting of one type than the other.
Vehicle fires are not very common anyway, but more internal-combustion engine vehicles than electric ones catch fire simply by being still the much more numerous form of vehicle.
Most such fires are of private cars, and unless they kill anyone or block a city-centre or umpteen miles of motorway, are unlikely to attract more than local Press interest.
Whether the fuel is petrol or Diesel does not seem to make any difference. Both fuels are highly flammable, but the fires are usually started by electrical faults whose risk rises with the age and general deterioration of the car.
I think fires in electric cars tend to attract more lurid reporting though, because they are fierce, very difficult to extinguish and the vehicles are still a fairly "new" type. "New" only in battery-type, really: there were many battery-powered private cars and small commercial vehicles in use a hundred years ago.
It may also be encouraged in some countries by a vitriolic division among motorists about internal-combustion versus battery-electric; apparently based on an unholy blend of domestic politics, fear of the new, and mere motoring snobbery.
......
There is a type of vehicle fire sometimes seen, in Britain at least, that has nothing to do with the vehicle's condition and everything to do with what it is carrying - or more closely, with what irresponsible people had added to that load.
That is of household waste in refuse-lorries, when some idiot has discarded a battery, perhaps within some electrical device, in the ordinary refuse-bin. As the bins are tipped mechanically into the compactor, and the waste is usually in black plastic bags anyway, the staff might not spot it in time.
There was one such fire recently in my area. Luckily the crew spotted the smoke in time to save the vehicle by tipping the load onto the road! They called the fire brigade while finding the electrcial appliance concerned, and removing it from the rubbish.
