Globally, there are lots of good helicopters to choose from. It all depends on mainly how much you want to spend, but also what type of flying you want to do now and in the future.
When you're looking to buy a helicopter, you've got to take into account a number of things. Some of these are:
There are different sizes of helicopter too. The size relates to the size of the engine in the helicopter. We'll discuss these now:
These are the little helicopters. They're nice and small which makes them cheap to buy and cheap to run. These are the recommended machines to start learning on because when you crash, they're not too costly to repair. Having said that, they'll do a all manner of aerobatics! Most people have a 30 or 46 for learning new stuff and simply cause they fun to bash round cause they're so nimble and cheap to run.
46 size helicopters are a step up from 30 size. They've got more powerful engines in them. Many 30 size helicopters can accomodate a 46 size engine, helicopters like the JR Ergo and Thunder Tiger Raptor are often upgraded in this way. However, true 46 size helicopters are often slightly larger than their 30 size cousins. They often have slightly larger rotor blades as well.
In the last year or so, 50 size helicopters have become popular. Mainly due to the increase in good quality 50 size engines from makers such as OS. Like 30's upgraded to 46's, many 46's will accomodate 50 size powerplants. Lately however, true 50 size helicopters such as the JR Voyager 50 and Xcell Fury 50 have started appearing on the market designed from the outset for 50 size engines.
These are the larger size helicopters. Until recently the engine size limit for competitions was 0.6 of a cubic inch which meant that was about as high as engine capacity went. Now that this limit has been revised, engine makers such as OS and YS have started bringing out much larger engines in the 80 and 90 size. Many people have started putting these power plants in their 60 size machines.
60 size machines are popular in competitions and for people doing lots of aerobatics. However, when you crash them, they cost more than the smaller machines to fix, so people often buy the 60's once they are confident fliers. They have the brute horsepower needed for some of the aerobatics people do.
Gassers are basically 60 size machines with petrol engines in them. The most popular petrol engine for helicopters is the Zenoah G23. Which is basically a chainsaw or weedeater engine. The benefits of these machines is that they cost so little to run in comparison to a glow helicopter. They'll often run for about 30-40 mins on a tank of gas. However, they are a bit heavier than glow helis and don't do aerobatics so well and they're expensive to buy. Repairs cost about the same as a 60 size helicopter.
My own personal experience
When you're first learning, I'd recommend getting probably a 46 size machine. The reason for this is when you deck them they're not too expensive to fix and they've got a good amount of power which mean you're less likely to get bored with it once you advance into aerobatics.
I myself have a gas powered machine, but I also have a 46 size for when I just want to go out and blast around the sky or try a new trick. I'm not as scared of decking the 46 as I am of the gasser.