I can agree with Savak's definition of full-service and GFE, but the definition of PSE doesn't match with my personal experiences. I have had the pleasure of providers who have engaged in what he defines as PSE in the context of a GFE session.
PSE to me is all about attitude, whether it is in the missionary position or a full on face-fuck. The best example I can give is a certain UTR latina who is the definition of GFE. On one particular occasion she had a voracious appetite for sex and used me like a sex toy. It was the only time ever I have reached release four times in a session, much less in one hour. But I had no choice in the matter. It was a rather plain session in terms of activities, but it was anything but plain in terms of intensity.
I don't think we can expect a certain menu item to be present based on a provider's claim of PSE service. I know several who make that claim that do not provide greek, but the sessions are certainly intense.
Of course, this is only my opinion, so you know how much it is worth.
GFE and PSE are NOT mutually exclusive! Slave, for example, is as PSE as I've ever seen, but has a GFE vibe to her. She so sweetly fucks my brains out...