The new features you get in 5.3 compared to 5.2 are
- The use Keyword
- Namespace Aliases
- Class Constants
- Namespaced Functions
- The Global Namespace
( obtained from http://articles.sitepoint.com/article/whats-new-php-5-3 )
If you don't need these features (or know what they are) and you have no developers requiring these features then there is not much benefit to running 5.3 over 5.2 from a SysAdmin perspective.
Both versions are supported in the sense they are getting security patches provided.
I would recommend you use PHP from the repos unless there is a compelling reason not to do so.
Managing security updates to software you have installed from source is a maintenance overhead and you are effectively putting yourself up as package maintainer for PHP on your system.