Ailerons on both top and bottom wings gives you a better roll rate. Because I do a lot of stunt flying I like four but two work very well. Most of mine have only had the two and usually on the bottom wing. I haven't noticed any difference having them on the top or bottom wing but having four of them is a big difference. If you opt for four then you just turn down the rates or add a bunch of expo. I didn't look but I think you can see four of them on my old Krier Kraft, I built that plane for learning IMAC flying so I wanted it to respond very fast in roll.