All the vol. with realflight have a verity of planes to choose from. I have all four vol. and do not fly all the planes. Since I like aerobatic planes, I like to fly the Cap 232, Extra 300, Edge 540. They also have a veriety of flying sites or you can make up your own.
I guess just figure out what your plane type intrest are and decide witch volume is best for you.
NEDYOB