Should I move to 2.5 or 3.1?
A familiar question today is which version of Joomla should I move to...
Since I have been migrating many sites over the past year or so, I have determined that as long as all of the tools are available, I will do my best to start any new (or migration sites) in Joomla 3.1.
If the site is using tools that do not have a 3.1 version (yet), then I will start with 2.5, with the intention of moving the site over to 3.1 as soon as I can. The next long term release is due out in Fall 2014 (from the last I heard), so you have time to make this decision. Remember the migration from 2.5 to 3.1 isn't as drastsic, and many of the tools that work in 2.5 also work in 3.1, so you don't need to upgrade each component the same way we had to between 1.5 and 2.5.
When selecting components in release 2.5 it is a good idea to try to find tools that will work in 3.1, because it means that the developers are trying to stay current, and the code is probably 'better' anyway. Any holes or defects from 1.5, just will explode if tried in 3.1.