Ghurd, it's all relative.
Some have the facilities to computer design these things and NC machines to produce them perfectly. They still have to decide what exactly to produce.
If you are investing a lot of time and effort into a 20 ft machine and have these facilities it makes a bit of sense to at least try for a tested aerofoil. If you have faith it will work better even if you have no means of proving it.
There is no doubt that perfect blades will work better than rough ones, if they are not all the same then they can't be the same aerofoil by definition.
With small things such as you make, other factors will have more effect on the output than the aerofoil section. If it is terrible then it may not work too well but if it is half reasonable then it will be ok.
It is perfectly true that some of the profiles need to made with extreme accuracy and need to be kept in near perfect condition. They are fine for gliders, model planes and man powered flight.
Some of these also seem good for wind power if you can sort the tolerant ones from the fussy ones.
While looking at one of the links to Selig's site I found that one of these highly prized sections is used on the Air 403. It does indeed put up an excellent performance at 30 mph, but the thing doesn't go round at 10 mph.
This is no criticism of the blade, just a wrong design philosophy for a land based machine, no doubt excellent for a boat at sea with good wind.
One thing that has surprised me in all this discussion is that after all the scientific discussion on the perfect shape we are advised to keep to tsr 4.5 .
I can believe there are real differences at tsr 8 and above between hand made things and proper sections. If we have to drop to low tsr to see any advantage then I expect your three sticks all different will still work quite well.
If DanB had taken a lot of trouble to make ideal blades for his 20 ft machine i don't think anyone would have seen a difference. How you extract the power and load the blades will make more difference than anything else. Siting and tower height comes next, then when these are all right then you can worry about blades.
If you are absolutely desperate for the maximum power in a 30 mph wind and can use it all or if you have a grid tie system then it makes better sense.
Where your interest and skill lies is largely a factor in what aspects of wind power you concentrate on.
No final answer, bound to offend someone, adopt the Zubbly approach, just do what you find fun.
Flux