For stable branches, there're even more differences. The release and support policy has changed as well, and the current policy states that there're two types of stable branches:
- Long-term support (LTS) branches: These branches are supported for three years for general bug fixes and two more years for only critical and security fixes
- Short-term support branches: These are supported for roughly one month after the first release in the next stable branch, LTS or non-LTS
At the moment of writing, 4.0 is the current LTS branch, with 4.2 and 4.4 planned as short-term support branches, 5.0 following as the next LTS branch, and all further LTS branches aligning to N.0 versioning. Will this hold? That's very hard to predict, so you might want to check the current policy at http://www.zabbix.com/life_cycle_and_release_policy.php.
How to decide which branch to use? Consider the available features and how quickly you would be able to upgrade. Does the latest LTS version satisfy you and you don't plan to upgrade for years? Stick with it. Really desire a feature in a non-LTS branch and plan to upgrade when the next stable branch comes out. Go with the non-LTS branch. Anything in between, and you'll have to make a decision based on the support policy that's in effect at that time. Here's a quick lookup table to help you decide:
Use a non-LTS branch when... |
Use an LTS branch when... |
You need a new feature in the non-LTS branch |
The LTS-branch features satisfy you |
You plan to upgrade to every new version quickly |
You prefer to stay with one version as long as possible |
You can tolerate slight instability |
You prefer a more stable version |
Note that the slight instability mentioned in the table doesn't mean that there're serious issues with the non-LTS versions. In some cases, more stable might mean this bug is pretty stable, but hasn't been fixed for a long time.