Never used Gaia but Basemap tracker does NOT work. My buddy 500 miles away from me was one of their beta testers is having the same issue. Mine hasn’t tracked properly in 6 months+. And the maps take FOREVER to download for offline use. One took over 35 minutes for me the other day. On full WIFI. The 3D map is cool but not available for download for offline use. Nothing better than OnX which is what I’ll be switching back to soon as I never had any problems with onX.
I am on our local Search & Rescue team and we use GAIA exclusively. It is the upgraded paid version. Works great, tracking is accurate. Able to share routes and waypoints is very handy. Most of our response area is out of cell range so I have our coverage area, the entire county plus surrounding area, downloaded to my phone. Was able to add all of Glacier NP when we were up there last year without issue.The various layers available keeps growing too. Overall I am very happy with it.
I have both Gaia and OnX. Can't comment on Basemap, never used it. OnX is a much simpler platform, Gaia is far more powerful but a bit larger learning curve. Map downloads are simpler and faster on Gaia even with lots of layers selected. There are tons of layers available for almost anything you can think of. The biggest part of learning Gaia is how to manage the layers to see what you want to see. The Gaia desktop interface isn't that great and can use some improvement in my opinion. I'm waiting to see how the goHUNT platforms pan out.
OnX or BaseMap if you want something simple and intuitive. Gaia if you are able to take the time to get passed the learning curve and have a bad ass layer setup.