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.

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

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.