That depends on what your current skill level is. Have you ever flown before? ever touched a tx radio...either in real life or simulators. Are you familiar with orientation, controls and the simple facts about how a plane works?

If you are an absolute beginner, then go with something like the Nexstar... (disable the auto level system thing). It's a big plane, easier to see, control, it floats well on low speed and has some extra perks to help a super beginner fly.

If you are familiar with the basics and you have tendency to learn quick, go with something a bit more in the moderate trainer category like say the Avistar. That's what I went with because I've been doing simulators, not just RC but MS Flight simulator since 1998 so i've got some experience when it comes to flight controls and orientation controls. It can be a moderate acrobatic plane after you are done training... that's why I went with it.

I see you were asking the difference between channels so I am assuming that you might be buying a ARF kit and radio separately, if that is the case, look into the Tower hobbies 40. It's a good plane and i've seen it fly, with it's high dihedral, it will float no problem and it very easy to fly from what I have seen.