From what I saw at Sun-N-Fun 2011 with the tornado (We got there the day after it hit), The short auger type are next to worthless, and the rebar at different angles hammered in was totally worthless, especially in the sandy soil down there. The Claw systems broke just outboard of the swivel bolts. I think with that kind of wind, something is going to give, whether it be a rope/tiedown failure or part of the airplane bending.
If you are wanting a permanent tiedown in the soil, I think the 3-4 foot long auger type would probably be pretty good, because they will be long enough to get down to fairly firm soil and probably hold better than most other things.
This is just what I have noticed and I am sure there will be some different opinions.