I seem to get pretty frequent updates on TestFlight. Maybe half of the updates indicate they are heading for the App Store.

TestFlight is great as it allows for more rapid bug fixes. Even if the fixes aren’t perfect it’s still good to see them improving and help where I can.

TestFlight is beta. Faster, more frequent updates, with a higher chance of receiving a broken update. Everything that comes to beta will go to the stable version eventually, once it’s polished and cleaned up.

If you like living on the cutting edge a little bit, and giving feedback to the developer, stick with TestFlight. If you’d prefer a more stable experience, and get really annoyed by bugs or issues, go with the App Store version.