Whichever one you prefer/is most intuitive for you!
You need to be comfortable with the setup you have, that way your flying will come more naturally to you.
Personally I prefer mode 2 for flying my quad because the right stick is simple in that it will 'bank' the model in whatever angle the stick is at, much like a conventional joystick. This is only my preference though, others will vary. It really is a personal choice/'feel' kind of thing. Neither is strictly 'better' than the other, its just what's best for you
