I'v had the sim that came with the Nexstar RTF. And I just recently bought the 4.5. I'm not much on changing the internal flight characteristics of planes and flying through and around an amusement part setting as the 4.5 lets you. It does have more screens for landing strips and such but after you've flown one plane their pretty much the same. I guess the Heli training is good as well, but Im not into those.. Not familiar with other Sims, but most are pretty pricey other than the Nexstar version that comes with the plane and radio.
Depending on your length of stay in this hobby, you'll probably want to go with a computer radio system. The disadvantage to the Nexstar is that the radio isnt one, and it is just a second radio to have around the house. However, after I learned on it, I'v used it to train other newbies as well as to loan them the Sim