I always think of GFE as a quiet evening at home with a girlfriend; some conversation, kissing, cuddling, hot and heavy action, followed by more kissing, cuddling (repeat as necessary).  While she is there you may really think she is your girlfriend.  

When I think PSE I think a higher energy "show", louder, maybe screaming, she's hot, and you both know it, she's showing off and she's just there to make you feel good. Okay so some guys may expect that out of their girlfriends...

But that's just me...