Too bad you're still forced to use Safari on iOS (in the US) even if you install Chrome or Firefox.
I wouldn't trust Chrome to treat my iPhone battery well, unfortunately. Looking forward to hearing reviews of real Firefox on iOS from Eurozone, though… I'd consider downloading the source and compiling with a dev cert if it turns out to be any good.
I wouldn't worry about a couple % of battery life through the course of the day. For me, it wouldn't be worth using a hobbled web browser.