RRT can spot and display for the GMA system as well as SOTA. SOTA cannot.
RRT shows a compass and the distance to the nearest SOTA summits, the first of which it can auto insert for you in your spot entry. SOTA Spotter has a function in a menu to list local summits but it’s not simply shown on the main screen as it is with RRT.
RRT has the ability to read out the new incoming spots to you so you know without having to look at the screen.
RRT and SOTA Spotter display posted spots. Both can filter which spots are displayed. I find the displayed spots easier to read from SOTA Spotter on a phone’s screen, especially in sunlight.
Which do I use the most? RRT. Why - because I am used to it and it ws around before SOTA Spotter.