Not really my definition, but generally it generally involves some degree of the following (not necessarily all)

Spitting on the shaft, DT'ing one's salami, some nasty DFK'ing with lots of exposed tongue action, anal intercourse, rimming and FIV/FIA, CIM and sometimes CIM/NQNS.

Of course, most real PS's use no protection per se, but any BBFS even in the PSE domain is downright stupid and dangerous. While one may resort to anything while in the heat of passion, the PSE with an escort is really not my "thang"

It is not dependent on specific services, for me at least, though I do have a few opinions on that matter as well. This is what I think of as a workable definition of PSE

I focus on the last word in PSE. Experience. For me, a PSE is more about the level of energy and intensity. In a good PSE experience (which I will be experiencing today with my favorite duo) I should have to ask for a break in the action to give myself any needed refractory period, to recharge. Otherwise, my little friend should never get cold and should be actively engaged the second  I either walk in the door or step out of the shower, until the moment he is out the door.

I do believe that a good PSE should generally include more services than one MIGHT find in GFE, but since the level of GFE is so all over the place I hesitate to say this is a "MUST". I have had some amazing GFE which includes DT, BLS, NQNS, etc. and I know some excellent GFE also offer greek. So basing GFE/PSE on services alone is pointless, IMO.

At the very least, and good GFE should not be phobic about the results of their actions (proper safety should be observed at all times). Personally, for me, I think PSE requires at least a BBBJCIM. Some DT and BLS, etc. should also be included. I would stop short of saying that salad tossing or DATO is necessary, but the tongue should be a bit more adventurous than your average lady.

Maybe the key difference between GFE and PSE? Your girlfriend wants to have sex with you, and she may even want that "creative finish", but for the GFE, it's the process of getting to the finish that she relishes. The time spent engaged in the acts, and the time in between the acts. A good PSE will make you think that the creative finish (CIM, COF, etc) is the only thing she cares about, and, IMO, this can't be accomplished with over-the-top theatrics or vocalizations. A good GFE will not act phobic about these kinds of things... A good PSE will act like she relished them (and convince you of it).

I am generally a twice in an hour guy. A good PSE can bring three in the hour. The times this has happened for me were Sonya & Ashley (reviewed) and Lola Vargas (not reviewed).

One person's PSE may be another's GFE.

I would think PSE would basically be a session that feels like a porn shoot without the cameras.  

For me, if I'm with a porn star and she behaves like she would in a video then I know I'm getting a PSE.

However, if her demeanor is different from how she is on camera then I know I'm getting a GFE.