I really only prefer the passenger side due to both our current cars having the fuel filler door there, and both future cars are that way as well. I can think of some pros and cons for both left and right, but maybe a less common pro for the right (passenger) is if you were to run out of gas on the street it likely puts you more out of harms way when refilling by gas can. Assuming of course that you are able to pull over where you're supposed to and are in a country that drives on the right.
