Well the Surround has a 1230mAh battery, and the Focus, a 1500mAh, so the Focus will give you almost 20% more battery life. Don't think there is anything that different on either device to affect battery life.
The Focus is rated for 240 minutes talk time. Talk time and screen on/browsing or whatever are about the same. So you can get through a full day on a single charge, assuming you are reading some email, taking a few calls, exchanging some texts, etc. But if you use your device to read news for a couple hours, play games and stream video, you are going to need a boost before the end of the day
Sent from my HTC Surround using Board Express