If you're leaning toward the 60 size, look at the Hobbico HobbiStar 60 MkIII. It has the semi-symetrical wing and is not so bad in the wind as a flat bottom and is easier to land since it doesn't balloon from the headwind and ground affects. The Avistar 40 is the same way in the 40 size. My students have had an easier time with those two when it came to landings. Not much difference in flight stability to the flat bottom other than you can advance to more flight stunts as your skill improves. Too many times I've seen the flats tip over and break a prop when trying to taxi with a side wind.