Content creators are urged to give the overall user experience first priority when determining the appropriate priority for new animations. Do not select the highest available priority simply because it seems like a good idea. Consider what users expect to happen when they sit on a chair, join a dance ball or ride in vehicle. Do they really expect to see your animation to carry on playing?
Used for many of the internal animation which are intended to be overridden with an AO.
Used for internal emotes.
Priority 2 is a good choice for stands in AOs.
Priority 3 should have been the best choice for walks, dances, sits and most other animations. Unfortunately many of those animations have been given priority 4 leading to unpredictable user experiences for creators who do try to use priority 3.
Priority 4 is used for many walks and most pose ball animations, such as dances, sits and vehicle driving animations.
Priorities higher than 4 should be reserved for situations when the objective is to override only some joints of the existing priority 4 animation.
For example, a handbag might override an arm and boots might override feet. In these cases, the alternative to a priority 5 animation is a script which continuously alternates priority 4 animations, generating a lot of unnecessary script events.
If you do not need part of the existing priority 4 animations to continue playing, you do not need, and should not use, priority 5.
The internal turn_180 animation, which plays during Edit Appearance, uses priority 5.
As priority 5 animations proliferate, a use for priority 6 is certain to materialize. However, as with priority 4 and 5. If your objective is not to allow part of an existing priority 5 animation to continue playing, then you can meet your objective either with a priority 5 or a priority 4 animation.
It is uncertain whether viewer and server support for priorities higher than 5 exists today or will continue to exist in the future.
You can view the UUID and priority of currently playing animations by selecting Advanced -> Character -> Animation Info from the menu, or Develop -> Avatar -> Animation Info on Viewer 2.