Spektrum is a premium brand and were long considered the go to choice in RC. Their transmitters are great quality and so are their receivers. There are also a lot of clone receivers for them as many people consider their receivers on the expensive side.
Recent years have seen a lot of competitors move into the market that make good transmitters at more affordable prices. Most of these transmitters use OpenTX, a powerful but somewhat complicated programming system.
- FrSky make the popular Taranis series, which I use. They have their own protocol and receivers, and a module bay at the back to add other protocols. I use their R9 long range module in that bay. You can also install a multiprotocol module for compatibility with other receivers.
- Jumper transmitters are more affordable and compatible with almost all receivers thanks to their "4-in-1" module that comes included. This includes Spektrum as well as RTF park flyers, toy quadcopters etc. Their receivers use the FrSky protocol. The most versatile out of the box.
- FlySky is not to be confused with FrSky. They are not OpenTX based and have their own protocol and receivers. Their system is the cheapest, but it's very functional and a lot of people use it.
You need at least 6 channels if you want to be able to fly quadcopters as well, for mode switching and arming. In the non-Spektrum brands, it's rare to see less than 8 channels now. Few people actually *need* 8 channels though, unless you are flying a very complex model with differential thrust, flaps, retractable gear etc.
Most of my receivers are just 4 channel on my regular planes, but I would not buy a 4 channel TX.
