What is the best AC receptacle on the market?

My opinion is that a tight grip is important, but not necessarily the major factor in a receptacle's performance. In my experience, for example, the Pass & Seymours have a very strong grip, stronger in fact than the Hubbell 5262's and 5362's that I currently use and stronger than the Hubbell 8300 (which I have also used) that the PS Audio is based on.

The tighter grip of the P&S (which I think is sonically inferior to the Hubbells), however, is a result of the design and configuration of the power contacts. This design gives it a better grip, but at the expense of the surface contact area that the power contacts make with the prongs of a male plug when inserted. While the Hubbells have less grip (which is still quite good in any relative terms), they will, by design, have a vastly larger contact area with the male plug. My thoughts are that this may be much more important than straight "grip", per se.

I have no experience with the Furetech, so cannot comment on its design or sonic characteristics.

As Lak says, the receptacle is always a factor. You should also take into consideration, though, that the receptacles in the PS Audio should be replaced, and probably the Richard Gray (I'm assuming that's what RGPC is-hope I'm not wrong). If you don't do that, you're only reaping about 50% of the benefit.