What do you want the aircraft to be good at? There are small trade-offs changing just about every aspect of your airframe design. Thick, blunt L.E. airfoils are better for slow speed flight, harriers, elevators, parachutes... thin, sleek airfoils allow for a higher speeds and better tracking at speeds generally with the tradeoff being a slight degredation of slow speed characteristics... enhanced tip stalling at low speeds, buffetting on the "edge" of a stall for example. Thick = better downline braking as well.

As said previously by 3DRC I too have found that the more taper in a wing, the better it snaps but the more likely it is to tip stall at lower speeds. L.E. taper back increases the same characteristics as chord taper over the length of each wing.

Large control surfaces are a given as well... the more there is, the more control in every aspect. Especially large ailerons, bigger is better for slow speed, harriers, rolling harriers, counteracting the torque while toque rolling to stop the rolling and hover stationary... need the ailerons to come as far inboard as possible to get them in the prop blast.

Heavy airplanes "tumble" better. Heavy can mean a big model with light wing loading or a smaller one with higher wing loading. Without weight, you lose inertia hence the plane comes to a stop when you change the attitude quickly, or changes the direction of the flight path to "follow the nose". With a heavier aircraft you can change the angle of attack or the attitude quickly but the plane has so much inertia going in the direction of initial travel that a quick change in attitude will change the planes attitude instantly but the direction of travel will be maintained for a short time. A constantly changing attitude gives you a nice tumble because the airframe never "locks on" to one given direction because it's not pointed any given direction long enough for inertia to catch up. So there is a plus side to light AND heavy, depending on your flying style and what you want the plane to be best at, its hard to make a little plane that does both, not till you get to over 25% scale or so it seems, then you start having enough weight to tumble good and still have light enough wing loading to 3D too.

Airfoiled tails fly more true I think, you can get away with flat airfoils on smaller planes to keep the cost and complexity of the average kit/arf down. Not very familiar with what actual benefits there are when comparing the two.

This is getting long so... There is no one design that excels at everything, there is always a plane that does x better than that one, but that one does y better than this one. You cant have the best of everything in one, thats why our sickness requires "another" plane constantly, "Oh look at what that one does!... sweet, I need one. Mine wont do that." And as fast as you get one that does y, somebody invents x and you now need a plane that will do that. Now, only if I had a bigger basement...