I had the S3 the day it came out and sold it 2 weeks later. Compared to the iPhone 5, the S3 is slow and laggy the phone is really choppy. The screen is great one of the best android screens on the market, but it does not compare to even the iphone 4s's retina display let a long the iPhone 5's.
I'm not saying the S3 is not a nice phone, it would be my 2nd choice. With the size, quality, polished OS, app store, and retina display. The iPhone is currently the best smart phone on the market. "My opinion"