Will a Flysky transmitter perform as well as a Specturm?
Yes and no!
Confused? You should be!
Either will work though the spectrum has a slight range advantage. Sadly with the spectrum you will need to pay more and buy the more expensive versions of the various product offerings. DO NOT use any single antenna Rxs in a fixed wing and try hard to avoid those Rxs that have little pigtail antennas as they can have their signal blocked quite easily.
The Flysky with its dual antenna system and long antenna leads allows you to get the Antennas away from everything and have better "Loss of Signal" avoidance.
For an entry level the Flysky has a full dual antenna system and is best bang for buck BUT the Spektrum has far far better performance when looking at longer ranges because of the satellite receiver system, (not with the cheap Rx offerings).
Most retail offerings in the BNF will require Spektrum transmitter.
At the end of the day you have to live with your choice. If you do buy Spektrum make sure you buy the latest versions of the transmitters< (dual Tx antennas).
Have fun!