I tend to try and use Safari when I'm at home just surfing the web or checking email because of battery life. If I'm not plugged in I will use Safari over Chrome. When I'm actually working I tend to use Chrome just because I enjoy the experience and have all the plugins I enjoy using there. Generally I am also plugged into a wall outlet when actively working in a browser (I'm primarily a frontend developer).

I just got the new tMBP 13" and have been making it a habit to use Safari over Chrome on it. It's a pretty noticeable different so far. I'm going to try and record some usage information over the next few weeks and see how much of a difference it really makes. In general though it appears that with Safari and general browsing I can get the advertised 10 hours or so. If I start using chrome (even just browsing) it turns to 7 or so hours.