If you looking for small.....got with the TREX 450. Great for indoors, but if there is a little more than a whisper of wind.....they will get blown around. If you want something a bit bigger look at the Century Swift. It's a .30 sized heli....but flies incredible. Parts availability has not been a problem, cost of those replacement parts has been very reasonable. Century also has a pretty good selection of metal upgrade parts...so if you want to bling it out you can. The main decision maker for me was what packs I could run. The Swift only needs a 6s1p maximum to really perform well. I personally went with 6s1p 15C packs to learn on and I've got a well powered setup that would be capable of basic aerobatics if the pilot was up to the task. To get similar performance out of the TREX 600. you are looking at 8 to 10 cell packs from what I've been reading. That is a lot more cost in just batteries and chargers alone.
I can't say enough how much I enjoy mine. I went from no heli experience to hovering and starting forward flight on all my own. Like I said...no previous heli experience and no outside instruction. I do attribute on other thing to my sucess though....and that's the video's on helifreaks' website.
www.helifreak.com There are full build video's in the tech room portion of the site and they gave a lot of insight and the proper way to setup the heli. He's done a lot of different helis so do check it out...it's worth taking the time to do.
Good Luck and let us know what you choose,
Neo