What would you recommend instead of the 3SX FBL?
For the more modern FBL units, you may be able to tune them to fly about the same, so FBL unit flying characteristics is no longer a major distinguishing feature. It is the other features that separate the FBL units from one another.
1) Computer operating system compatibility. Mac? Windows? Linux? Virtually all FBL units are compatible with Windows. Spirit, VBar, and a few other units also run on Mac.
2) Reliable Self-level and/or Rescue feature that is pretty vibration insensitive.
3) Internal governor.
4) Integration with one or more transmitters. This makes it so you can make most or all adjustments via the transmitter without the need of a computer.
5) Bluetooth or WiFi option. Some units use a separate module. Some newer units have the BT integrated. This makes it so that you can make most or all adjustments via your phone.
6) Telemetry integration. Newer units are able to "read" the telemetry data from the ESC. This means that you would not need separate telemetry modules that tend to be bulky and/or expensive. With this option, the telemetry can tell you when a predetermined battery capacity is consumed, so you can fly until that battery capacity is consumed. This is more valuable than the flying timer.
7) No need to purchase "Pro" software to unlock all the features. Some units require you to purchase the "Pro" software to unlock all the cool features. Other units just include the software for no additional charge.
7) Under $200. Many of these units with all the cool features list for under $200. Customary discounts also apply.