I am thinking of getting one of those twin blade helicopters.

What is the difference between 3 and 4 channel?

And which one is the most stable, easy to fly etc?
I am more interested in scale realism, to fly inside the house

price?

more channels, more control... generally speaking. eflight makes some great ones, CX2 and CX3 are well sized coaxial helis, great parts support, outstanding build quality, they are actually 5 channel, but the 5th channel is for turning an optional navigation light accessory on and off.

they have a smaller model also, MCX I think it is, its a micro size, in a dead calm day you can take the CX2 and CX3 outdoors, micro is indoor only.

Price wise, the cheaper the better... but up to maybe $150
Parts + looks + ease of flight are the primary concern.

Also, how many more controls are there? Besides up/down, left/right, back/forward?