Wow, no replies?!
Partly that may be because the Imp and PSK are fairly different. Both are fine for a pocket carry, although the PSK is easier since it's smaller and lighter. Personally -- and YMMV -- I prefer the PSK since it "makes sense" in this size package. I have the original version, .09" Sandvik 12C27 w/Kydex neck sheath, which is featherweight at sub-2 oz. Thin stock cuts nicely and is tough enough for anything short of hammering it into a steel drum and other kinda dumb things for a knife. A newer version comes in thicker stock 154CM w/Pocono sheath; I don't have it but it's slightly more robust acc. to specs and apparently still very light. The Imp is beyond overbuilt IMO at a hair under 3/16" convex A2. That's OK if you want "indestructible" (e.g., I'm sure you could hammer open a steel drum w/it if that's your thing). Main thing I don't care for is the Imp's shrunken "Pro Series" style handle w/that slight bird's beak at the butt end that I find uncomfortable in actual use. It's bigger and thicker than the PSK handle but the design of the latter is much more comfortable and versatile for me.
I don't have the Seax either but it's obviously not comparable at all to the other two. I don't IWB my knives so hopefully someone else can address that for you.
My two cents but, again, your mileage may vary --
Glen