On both transmitters there are huge topics and also some topics about which choice is better.
https://www.rctech.net/forum/radio-e...utaba-7px.html
https://www.rctech.net/forum/radio-e...tl-pistol.html

About SBUS there is a lot to find on the web:
https://www.rcmodelreviews.com/futabasbus.shtml
Simply explained: it is a serial network connection, one connector connects all (sbus electronics) but servo's can also still be connectet to own normal PWM outputs.

Sanwa: expensive receivers, cheap sensors (sensor electronics are inside the receiver)
Futaba: cheap receivers, expensive sensors (due the SBUS electronics in the sensors)