I used onx this year and will continue to do so. Had Garmin continued development of their hand held gps units after the Montera, building on those advancements, there wouldn't be an OnX, but they stuck their heads in the sand. The market has left them in the dust and I suspect their hand GPS units will be a thing of the past shortly.
If you're computer saavy you can add any map/sat imagery to a garmin that can be put on the phone, but why go thru the hassle? OnX has a ways to go with their web map but they have a direction and are looking forward.
I prefer gaia to Onx maybe just because Ive used it more. We used gaia to take us back to our hammocks on a pitch dark no moon night. I dont know the +\- yardage but it did a dam good job.