I'd have to say battery... if I didn't have a charger for my car. Having that, I don't see what the battery life matters, plug it up and let it charge if it's that big a deal. That's what I don't understand about battery complaints, maybe I'm missing something, if you got a charger then what's so terrible about just plugging it in?
USB on your computer at work... plug it in and let it charge. Wall adapter for USB, plug it in and let it charge. Car charger... plug it in and let it charge. If I were out walking in the woods or lost where there was no place to plug a charger in, then I could see the life of the battery being an issue. But, if that were the case I don't think I'd be walking around surfing Google or just carelessly using the phone's available charge...
Just my 2 cents...