usually, in beta versions, there are newer features that haven't been pushed out to the stable version just yet, which also means it is subject to change.
on the stable version, updates are final and glitches and problems are less likely.
basically, it's the same thing, but you're more likely to run into a glitch/new feature being tested out on the game with beta release stream. it's often a little slower than cutting edge but the features have been verified/tested a little more.