My 2 cents is that OnX Fish is geared towards scouting lakes - think one-stop-shop for stocking, surveys, info about the lake and what's in it. Their maps are NOT for precision from what I've seen. Most other dedicated lake maps will blow it out of the water (no pun intended) but they won't have the additional info that's helpful when scouting.
If you fish the same lakes and are already familiar with what's in it and you just need detailed maps - go with a dedicated mapping app. If you're scouting new lakes, adventuring, need a rough idea of the lake structure - OnX Fish will help you.
I use Garmin Active Captain and like it - it's synced with my waypoints from my Livescope. I plan to try OnX Fish to find some new lakes in my area for late ice season.