There are three things you need to pay attention to when purchasing these entry level helicopters.
1. Number of channels. 3 channels move up/down, rotate left/right, and go forward/backward. 4 channels add in a slide left/right. The fourth channel ads a considerable amount of maneuverability. I would recommend starting with a 4 channel. Yes, they are a little bit more difficult to learn, but the layout of the controls is different than a 3 channel so if you start with a 3, you can't just move up to a 4, you have to completely relearn how to fly it. And don't let the X.5 channel throw you off, the ".5" is a marketing ploy, I really have no idea what it means... a 3.5 channel is the same thing as a 3.
2. Fixed pitch vs collective pitch rotors. A fixed pitch helicopter as two blades that have fixed to a motor, each spinning a different way (which they refer to as "coaxial"). There is a third tail rotor mounted horizontally that lifts and lowers the tail to provide forward/backward movement. A collective pitch rotor the pitch of the blades float on a swash plate that changes the pitch of the blades alowing a greater level of control and enabling side to side movement. Collective pitch helicopters are much more maneuverable and enjoyable.
3. Radio Controlled vs Infra Red Controlled. IR controllers use an infra red beam of light to send controls to the copter, same as a typical tv remote. This means that you need to stay line of sight and you cannot use it outdoors in sunlight. RC controls use a radio signal giving you a much greater range and can be used in bright sunlight. To tell the difference, IR transmitters have a little plastic dome on the top of the controller. RC will have an actual antenna, though it may only be a few inches long
With all of that said, I would strongly encourage anyone getting into it to buy a 4 channel, collective pitch, RC helicopter. They are much more enjoyable. 3 channel, fixed pitch, IR copters are slow, have poor maneuverablity, and just get boring quickly.
Another thing to mention, make sure the helicopter you buy has readily available parts. As durable as any of them claim to be, eventually parts will break. Most of the time, these parts are dirt cheap and simple to fix... but that's only if you can find parts for it. It would be best to google the model number + "replacement parts" to see if they are readily available.
To answer a previous question, flight time for these type helicopters is usually in the 10-15 minute range. I'm not familiar with these particular brands to say exactly.
When what to my wondering eyes should appear, but a bucket of wings and a six pack of beer!