I'm curious and not intending to start any kind of Ford versus Chevy flaming war... What are the advantages of the Spektrum brand? It seems to be the most common here on the forum and even in the AMA club I'm joining. Not knowing any better I bought a Flysky FS-i6X for less than $60 that has 10 channels. I've just put in my third airplane and it seems to have any ability I can think of. Have already used dual-rates, exponential, elevon and flaperon mixing. The Spektrum looks like nice hardware, but the Flysky seems to have metal bearings in the sticks and doesn't feel like I'd wear it out in my lifetime.
I started with the FSi6X as well. I found it quite capable and versatile. I have since gone over to the RadioMaster TX16S w/ EdgeTX. I have no experience with the Spektrum radios.
The FSi16X is limited to 2 mixes, 20 models and the resolution of the gimbles is not great. it uses AA batteries which has pros and cons and is generally not as robust as the higher priced radios. The FlySky compatible receivers are inexpensive, reliable, and readily available. I did have one 2 position switch break, but it was easy to replace, and I do not think the switches in the more expensive radios are any stronger. I do still think it is an excellent value and a great starter transmitter.
The RadioMaster TX16S feels much smoother in operation with it's Hall Effect gimbles( I will be upgrading them to the AG01 CNC gimbles at some point), uses either a 1s LiPo battery or 2 18650 Li-ion batteries in the included adapter. The EdgeTX(or OpenTX) firmware, basically gives you unlimited mixes and models, though it has a fairly steep learning curve. Once you understand the platform, it's amazing what can be done with the logic switches and special functions. The multi protocol module lets me use all my Flysky receivers and, virtually any other receiver on the market as well. It is also easy to update the firmware as new releases become available. You can also use ELRS external modules if you want to go that route.
I know you specifically asked about the Spektrum radios, but I just wanted to address the differences in hardware quality and capabilities between the FSi6X and another higher end, yet still modestly priced radio.