My co-worker has the GS3 and its a pretty nice phone, super light, great display, etc. You have to look beyond iOS vs Android OS or at least I do when I compare hardware for performance purposes.
My position is I will get the next iPhone unless its a total failure of product engineering, and yes that could happen though not likely. The biggest draw to iOS for me is the timely updates to the OS, that is important to me and sadly is a critical factor Google did not take control of when they open sourced their OS. Between OEM's and Carriers you just can't count on getting the current OS for at least 9 months IF at all. I expect my phone to be useful and relevant for at lest the 2 years I am on contract.
I know vast majority of users are not like us when it comes to OS updates but then again I do miss hacking and modding my prior phones.