I don't think it's a question of deltas being faster...it's just that a guy can buy a Diamond Dust kit or Whiplash ARF and go faster than about 98% of the people he flies with for a pretty small chunk of change.

Of course you can go faster if you get into the $700 F3D racers or the like....or faster yet with the giant scale racers. By then you are up to a $10K aircraft.

Or go about 90% as fast for a couple hundred dollars, no rules to build by, etc. Just my view on the situation.

Looks Like Dennis' son has a good idea about how to go fast without an expensive plane..it can sure be done. I just bought a book on low drag airfoils and drag reduction. I plan to build a small plane someday, but I can't build it as fast or as cheap as a Dust. Or look at the Magnum, not extremely expensive but moves right along.