If you're really concerned about battery life, go with the BB. When I had a G1, I had to charge it once a day, no matter how light the usage whereas with the 8520 I charge it once every 3 days on moderate usage.
9530 v18.104.22.1689-took a dive into oil...
8520 v22.214.171.1241-in the box
8100 - 126.96.36.199-out of retirement? lol