It has new features, including (video!) streaming of minor league games.
"MLB Audio is now At Bat -- and has a lot more than just audio
For 2023, MLB Audio has a new name: At Bat. Why the new name? Because this subscription also has a lot more to offer than just audio for this coming season.
MLB At Bat subscribers can still listen to blackout-free audio broadcasts of all MLB regular-season games -- with their choice of home or away broadcasts and alternative Spanish audio, where available.
What’s new for this year is all the video now available as part of this subscription. At Bat subscribers will be able to watch live video of Minor League games in the First Pitch app and the MLB apps -- the same as MLB.TV subscribers. At Bat subscribers will also receive access to subscriber-only content like MLB Big Inning, our daily whiparound show with live look-ins and real-time highlights, as well as access to our library of subscriber-only video on demand originals and documentaries."
https://www.mlb.com/news/mlb-tv-has-new-feature-in-2023