Hi there,
Going from a CPP2 to a 400, 500, or 600 class heli is really nite and day in terms of stability, maneuvering, handling, etc. Size does matter with heli's, and equally important is the quality of the electronics you put into them. The gyro, tail servo, motor, ESC, and cyclic servo's really do make up a good part of the heli. Skimping in these area's does create a handicap from the start, esp when you start crashing a heli b/c a particular cyclic servo goes bad in flight, or some other similar electrical failure.
Please don't get me wrong with this next statement but Eflight is great for the beginner heli pilot. They offer relatively ready to fly heli's for a catchy price. However, many of those components in the heli need upgrading before too long and so that low price does go up eventually. One idea is to move away from the ready to fly heli's and into the kit heli's. One way is to get a barebones frame kit clone (such as HK, EXI, or Tarot) and then add your own electronics to finish. This gives a heli that has the electronics you want, not what a particular manufacture decides on. It also gives the pilot the experience of building and setting up their own heli, from the ground up, so to speak.
Well, just wanted to add my 2 or 3 cents to the discussion.
Mark