Considering the number of such stations, explosions are rather rare, although one did recently explode in the USA. It turns out to be difficult to get a decent explosion out of bulk liquid petrol. Even setting it on fire is not as easy as some think. Try it with liquid diesel, practically inert. What you really need for a good time is empty petrol tanks.
If it exploded; the outcome would have been pretty much the same, but i'm probably wrong. I assume the amount of KJ is about the same; hydrogen will blow up much faster and much more violent. Petrol tend to "wooooof" into an fireball and expell a lot of the energy in the fire afterwards.
A leak in the petrol tanks at a station won't cause explosions in itself, it causes polluted ground water. Not to mention it's quite hard to get petrol to blow up, you need a pretty specific mix of fuel and air.
Hydrogen pretty much blows up no matter what if there is a leak.