I "upgraded" from the Spectral X to the dongle. Less wiring is nice, and the app joins several other controllers on my cell phone. I think that the user interface on the dongle is just a copy of the Spectral X user interface, but I never actually compared them side-by-side. I'm not sorry I upgraded, and I had no trouble selling off the Spectral X.
I haven't used the dongle, I have the controller. It's fine. It works. You set it up once, then forget it. The dongle is ugly. These days, you really shouldn't be paying $100 for basic WiFi functionality, but it is what it is.