collects more data => takes more battery => battery will last shorter than with the one that comes with windows.
Don't know if that makes a noticeable difference but just a thought.
battery behavior itself is unpredictable. the battery have a hardwired "software" that tell windows how much juices it has. batterybar just redundantly doing the same thing, plus some cosmetic that will eat up more juice, and make the battery more unpredictable.
I'm gonna have to disagree. BatteryBar is very accurate on my computer. It doesn't take up more "juice". And yes, it looks nice. But that's the whole point of it. I wanted a visible display of how much battery I have left. Which the windows does not do, and the windows one is less accurate.
I prefer BatteryCare, it's completely free and it has more functionalities.
As for taking up resources,
In my case I've 4 GB RAM, and it take up to 4 MB. As for CPU normally 0% some times 1%.