Hi,
It depends how daring you are. In general, master is the current release (presently v4.5.1) and development is where the next release (currently v4.6.0) is being developed. Once the development code is ready for release master is updated from development and the release is made from master. Sometimes you will find changes are made to master after a release, these are typically minor changes or perhaps because an urgent minor release is required to fix a specific bug/issue. Alpha and beta releases are taken from development whenever development is at a stage where we want some user input. Issues/bugs identified by alpha/beta users are fixed in development and another alpha/beta release made if required. The process repeats until release.
In summary, master is typically stable and is generally the last release (or very similar). Development is more bleeding edge and likely to contain bugs, or is more subject to change; the number of bugs typically reduces as the code matures. If you want to try some of the new features of the next release, or need a particular new feature of the next release, use the latest alpha/beta or the current development branch but be prepared for bugs and changes. If you want stable use the current release. I would only use master if you need a specific fix that you know has been applied to master since the last release.
Gary