One is not exclusive of the other, Norb. They do similar things and different things as well. Litchi is feature rich with things that are not available in Go4.
1) With Litchi, you can, from your computer, program an automated mission and do a virtual flight of it from home, making tweaks before you get out into the field. Once satisfied you can go out to the location and load up the mission and fly it actually. Additionally, the Litchi mission hub has thousands of other missions that people have flown that you can download and fly yourself.
2) Litchi will allow you to fly FPV (first person viewing) with an inexpensive pair of VR
Goggles. It's not like flying a dedicated FPV drone, but a pretty amazing experience nonetheless. It also has a side-car program, LitchiVue which supposedly allows another person to view the flight in a second monitor. That feature isn't so great. FYI the DroneVR app has this same ability, has some other features and 2nd monitor capabilites as well. I think $10 for a single drone license. I have both apps.
IMO those are the main two stand-out features that I use Litchi for. There are easy to follow tutorials to get you started.