I think the PSE is all about the higher level of enthusiasm and involvement from both the SP and consequently the punter. GFE is a more relaxed, gentle, polite session. DFK, semi submissive sex, cuddling and all that. PSE should be no-holes barred. The type of dirty sex you get when you pull a girl in a club for a one nighter. Frantic DFK, fingering, OWO, dirty talk, toys, squirting, deep throat, gagging, hard sex, anal, swallowing and the overall impression that the SP wants to fuck your brains out.
At least that is what I think a PSE is/should be.
Very few SPs out there offer this definition of service though.