Kermit - I can't speak for everyone, but my co-workers tend to have Prados and Hiluxes with diesels. I'm the weird guy with the FJ. At least anywhere near Sudan, petrol is so cheap that there's essentially no price difference. While the diesel sips a little less than the petrol motor (okay, a lot less), the petrol motors are not that terrible on fuel. I keep four 20L NATO cans on the roof, and I've never really been afraid of running out, even in some pretty remote places. The petrol is substantially quieter, which matters if you enjoy seeing wildlife and, more importantly, if you like being able to pull through a village without causing a stir. My FJ is one of the quietest trucks when I'm pulling up to any market, truck stop, etc. Maybe the thing I like the most is that petrol has octane ratings associated with it and is run by all the motorbikes in the region. This means it's generally of higher quality (in my experience) than diesels. I've actually never, in over a year of driving in East Africa, heard of someone getting bad fuel. But I've heard plenty of nightmare stories of contaminated diesel. Ex-military Mercedes trucks and two-ton Tatas will gulp down stuff that will stop a consumer diesel motor in its tracks. Also, the number of people using gasoline for motorbikes, small cars, etc. means it's "fresh" at any name-brand station (Shell, Libyoil, Total).
But... if I'm being honest? A lot of it is just preference and what people are used to. Definitely never thought it was worth it to do a full drivetrain swap in either direction (petrol to diesel or diesel to petrol) unless you've got a dead motor and a good reason. Both engines are good, and, like dogs, it comes down to the care and feeding more than the starting genetics.