Originally Posted by TenoBell
That depends on how they tested it. Here is a more thorough review of the unibody MBP battery life.
The 17" Dell Studio quad-core Intel Core i7 machine gets only 3.5 hours with an 9-cell, 85W battery on a WiFi test in at least one independent review
. That is larger than the MBP's 73W battery and the significantly larger than the 56W battery used in the average 15" Dell Studio with the default battery size.
It's hard to find reviews on the Dell Stdio 15 with the 720QM, but there are plenty of other machines with reviews. The 6-cell battery life is the downfall of all the ones I read. The machine is already excessive without adding a decent 9-cell battery that still doesn't outlast the MBP battery. Part of this is Windows fault as they Mac OS X is shown to have much more efficient power management, but that would make you think Dell would be concerned with a little more.
I'm always amazed at the people that think that Apple should put the fastest possible processor into their machines without considering the size or weight of the chassis to maintain a decent battery life. The current systems are finally getting into a good place with battery duration, but I won't be happy until 12 hours of WiFi use can be had, which will meet my average mobile day needs.
Note that Apple also uses li-poly-ion batteries, which I think allows for more power in a smaller size and weight than li-ion batteries. (I'll have to check into that, can't remember everything all the time)