These are both much debated terms. I believe a good general definition would be:

GFE is when the session makes you feel like it isn't a business arrangement but on some level it is also chemistry.

PSE is basically acting out your favorite porn video in real life.

gfe=girl friend experience
pse=porn star experience

you want a nice friendly relaxed time, thats the first one. some to more/better degrees than others
and that falls under Your Mileage May Vary (ymmv)

play safe
Nicole