When Apple launched the new iPad 3, they also made some minor updates to the iPad 2, and it would appear that the new version of the iPad 2 comes with improved battery life over the original version.
The guys over at Anandtech have been testing out the battery life on the new iPad 2, and have seen battery life improvements of around 15.8 percent for web browsing.

They also managed to get a 29 percent increase whilst playing games, and around an 18 percent increase for watching videos, you can find out full details on the tests over at Anandtech.
Source The Verge