if you want to use flutter for production app then many developer and even google recommend to use stable . if you are using new feature and all feature that flutter provide that I would recommend master but not for production only for hobby project and improving your flutter skill and testing new thing that flutter provide. and not available in flutter stable.
now to know which branch you are currently using.
open terminal and type the following command.
flutter channel
It will show branch with start in front of it. that is you current branch
to change the branch you can simply use this command.
flutter channel ChannelName
use respectively channel name and hit enter and then run the below command
flutter upgrade
it will download all the require file from flutter GitHub and you will be ready to go.
all possible flutter channel are below.
master
The current tip-of-tree, absolute latest cutting edge build. Usually
functional, though sometimes we accidentally break things.
dev
The latest fully-tested build. Usually functional, but see Bad Builds
for a list of known "bad" dev builds. We continually try to roll
master to dev. Doing so involves running many more tests than those
that we run during master development, which is why this is not
actually the same to master.
beta
Every month, we pick the "best" dev build of the previous month or so,
and promote it to beta. These builds have been tested with our
codelabs.
stable
When we believe we have a particularly good build, we promote it to
the stable channel. We intend to do this more or less every quarter,
but this may vary. We recommend that you use this channel for all
production app releases. We may ship hotfixes to the stable channel
for high-priority bugs, although our intent is to do this rarely.