I begun using homu before switching to bors-ng. I’ll speak from my experience as a fellow user.
Both projects strive for the same goal - to maintain an evergreen master by testing merges on staging branches before merging them into master. Both projects use Github PR comments with nearly the same syntax to trigger approvals, halt testing, or try a merge.
While both projects can be self-hosted, homu’s free SAAS option is now defunct while bors-ng’s is alive and well at app.bors.tech. If you are looking for a plug and play service, this is probably the route you want to take. Both Travis CI and Appveyor are supported out of the box (see the getting started guide). If you hope to self-host, both homu and bors-ng are viable.
The main differentiation between the two projects is in architecture and development. Bors-ng is written in Elixir and principally developed by @notriddle with community contributions. To my understanding, homu has migrated to being maintained by the servo team, mostly for internal use. In my experience, the bors-ng project is quicker to respond to issues and is seeking to reach a wide range of projects.
Hope this helps!