Diesel fuel, while slower than gasoline to actually burn, burns with much more intensity and heat than does gasoline once it does get going. Diesel's a bigger PITA to put out once it goes up in flames for that reason.
Even still, gasoline by itself doesn't go boom all that readily -- you really have to combine it with air/oxygen to make it ignite. That's why gasoline vapors are much more dangerous than liquid gasoline.
You can even throw a match into a puddle of diesel fuel and the match will go out -- there isn't enough heat there to ignite the diesel. If you throw in an ignited flare, however, that's plenty of heat to get the diesel going.
I'm sure DLRPyro can explain this mo betta than I can.