Not that I'll do much to dispell the "dork image" that we're talking about, but as a kite designer/builder in my spare time, the idea that a foil is inferior to a tube kite is absurd.
1: Shorter leading edge = less drag = faster kite.
2: Twin skins provide a cleaner aerodynamic profile. The fact that there is no blend from the LE tube into the kite's skin means it leaves a turbulent wake where a foil profile smoothly exits the wind.
3: To argue that the bridle on the foil is some major aerodynamic issue is retarded, especially in light of the whole SLE movement with the addition of bridles.
4: Safety. Given the proper design, a foil will be unable to generate pull when the safety is engaged as it does not maintain a shape that can generate any significant amount of power.
I saw a Speed up close for the first time about a month ago, and I can't say that I've ever seen such an elegantly conceived and well executed design. It looks like the wing of a jet plane by comparison to a typical LEI.
It's been mentioned already, but with the SLE kites gaining so quickly in popularity, it seems like the convergence is that tube kites look more like foils each year, not the other way around.
Finally, the notion of "the market" selecting the optimal design is asinine. There are dozens of examples of the market selecting technologically inferior products. VHS vs Betamax, anyone? The only valid argument so far is that since there's so few foil flyers, that getting an assist at the beach is more problematic. But if FS can somehow lower the price of their kites, that problem might progressively go away.
As with anything kite-related, the end point is always that people have different preferences and there are many different designs that appeal to many different sets of requirements. As with anything people-related, we tend to speak out of our asses based on incomplete knowledge. Maybe that's why yokels out in the sticks tend to be more homophobic and anti-science than a citydweller. If you never see it, you never have to try and understand it.
OK. That's my rant. Carry on.
-J