What I've noticed is that the fuel door is always opposite the side of the exhaust -- many exceptions of course, like dual-exhaust, duh.
Personally I prefer passenger side.. Why? Because the hidden bollards at gas stations you don't see that you sometimes open the door into (they're usually low and below the window sill, sometimes clearly visible). It's not because I wasn't paying attention, it's because they put them in a dumb spot!
But that reminds me when I have a car-full of kids, they'll open the passenger door(s) into the bollards if the filler was on the pass. side.
So my "expert" opinion is passenger side for my personal car, drivers side for any vehicles I might carry my kids around in. If anyone knows any designer in Detroit / Japan / wherever cars are made, please forward this advice to them. Summary = any car that only I drive, pass side. Car with kids = drivers side.
I'm 4/4 for vehicles with fillers on the drivers side. I never have to guess at the gas station.