If battery capacity is your main issue, you can do better with an aftermarket one. I got a 4500 mAh for my Galaxy S3 for $30! Of course, it requires a new case because it's enormous...
It wasn't my main issue, until I got it. I was very restricted with my Samsung before, because I would always end up with dead battery during just a one day of intensive usage. As for the size, it's absolutely manageable, maybe a little thicker than most of the 5" phones.
