The turbo boost i7 chip makes it stand out from the others. Download the demo here

http://www.intel.com/technology/turboboost/index.htm?iid=tech_product+tb

Battery life is also influenced by the graphics subsystem. Integrated vs discrete. Here is a listing of current chips: http://www.notebookcheck.net/Comparison-of-Graphic-Cards.130.0.html Higher perf. generally means less battery life.

Third thing is #of cells in the battery: a 3 cell has less capacity than a 12 cell.

Last thing is LED backlit screens take less juice than CCFT screens although both can be dimmed down.

You have to look at the overall system content & what your's doing. A netbook with an Ion chip and solid state drive SSD has little heat and no fan. Might run all day. A souped up notebook running a game may need the wall socket in an hour.