Differences between the 7.x-2.x and the 7.x-3.x branches

7.x-3.x was started to create a better plugin system, and to make it more OOP so others can easy modify the plugins or create new ones.

Also the field implementation is more robust and the profiles structure is changed to not be directly connected to a user role.

And to be honest, I'm not sure what else is different as that branch was created almost 1,5 years ago, and my current situation as Drupal developer has changed over the time.

I just know that 3.x is more "nice" then 2.x.