Hm. I don't typically apply fantasies to my adventures into tickle land; that is to say, when I tickle, fantasies aren't high up there. It's like, ZOMG FEET, HAVE AT THEM! RAWWR. That's enough.
But then I also enjoy creating my own experiences, which was what led me to writing tickling fiction to begin with; I wanted my own, specific tickling fantasies to become real to an extent, since they were so absurd/out there... and the only real way was through a creative etc. But I can't draw, so had to be writing.
Costumes are great, though I never employ them, but... well, I dunno. I can't say an achievable fantasy is better than a complete fiction fantasy because although the two seem comparable, I don't think they actually are. They really do sound like they should be, since they both fall under the ideas of sexual fantasy (or not sexual, whatever), but I would argue that there's a lot more going on than that. Complete fantasy is a broad term that can refer to things that don't exist, the theories of physics working differently, specific tools that don't exist, organizations that opt to tickle instead of use any other method, super ticklish lee's, and in general a world that caters to the whims of the author/audience. Like, someone mentioned spy tickling, and that is a far more real example than, say, a plant which derives some sort of food/energy from women by tickling their feet, and in that regard, I think that the complete fantasy should be better because it's more open, but even then, if that's only going to make you dream of things that could never exist... then it could also be argued as a point against it.
Both have merits I suppose, but yeah, since fiction allows for what cannot be.. I kind of want to go with that.
As an aside (to op), I enjoy the picture in your sig. Dude. Seriously. Flowers in hair are so rare o-o. Kudos.
Etc~