Welcome to AF, Jabanero!
You might try calibrating the battery by using it until it dies a few times, and then recharging to 100%. It doesn't always work, but it can't hurt.
I have two S3's, US version, one with AT&T, and one with VZW. The battery life could not be any different, if they were two different phones from different planets! The VZW S3 makes an entire day, and when I plug it in around 7pm each night, it still shows about 80% battery left. The AT&T S3 gets unplugged the same time every morning that the VZW S3 does, and by 5pm each night it has anywhere from 20% to totally dead battery. I haven't figured out the difference yet, still working on that.