RE: Which One ?
If youve flown helis before, look for a heli with a belt (or shaft) driven tail rotor.
Ive have a Kyosho M24 and I wouldnt wish it on my best friend.
Ive found the tail motors to be less precise and burn out easily, especially if your likely to try and upgrade.
The Trex 450 has a proven record and parts generally less expensive than many others.