Do you have neighbors? If so, you will really only be flying a nitro heli at a club field. That is not a bad thing. But certainly not as frequent as are opportunities for electrics.
The T-Rex 450 can handle a little more wind than the CP.
The T-Rex 600 is the same size as a 50 sized nitro. It can handle a lot more wind.

What transmitter do you have? If I knew that I was going to continue on with the hobby, I would invest in a good transmitter.
What is your budget like?

Vince