I can fill you in on my experience..
I have had a total of 3 Galaxy S3's because i could not make up my mind so i went back and forth over the course of the 3 months.
June - I had a Iphone 4s, Pre-ordered the sIII the first day it was availabe and got it the Friday before the 4th of July i believe. Initial thoughts were it was a very nice phone, loved it...Then stuff started to bug me. Colors are WAY over saturated, almost comically. Battery life was much better the Gnex i had tried (3 times again) but still not good enough. I was getting about 3 to 3 1/2 hours usage time, almost all of it is web browsing/email. Screen absolutely sucks outside in sunlight, i mean bad..really bad... Sold the phone and went back to the 4s.
July - Started thinking damn, this iphone 4s's screen is tiny. I did love web browsing on the S3, especially at night while in my house. So i got another one off craigslist. Tried it again and the same things started bugging me again. This time i knew what the problems were, but i wanted to see if i could live with them again... Battery life, i think i could have lived with, although on the weekends it would run low come nightime when i would be out and about. After that all the other stuff i mentioned again popped its head up and i sold it off again after about 4 weeks..Went back to the 4s.
September - Started thinking about the damn thing again..picked one up off craigslist again, within about 24hrs though this time i knew it just would never work. The AMOLED screens are just not my thing and will never be. They are just horrible outside...Sold it about 48hrs on craigslist...back to the 4s.
A week or two later i picked up the iphone 5...
Pro's - screen is beautiful, not because it is bigger(which you cant even tell it is bigger really than the previous gens) but it just looks like everything is floating on top of the screen. Pretty cool.
- Best outside performance i have seen of any phone
- Battery life is unbelievable for a 4G LTE device, they only increased the battery size from 1440mah to 1440mah or something and I get 5-6hrs screen on time, 80% web browsing/email, the rest is app usage that requires internet. Unreal how they were able to achieve this, i would say it is because of sharps new LCD screens that are super energy efficient, along with new 2nd gen LTE radios, apple is also only using one LTE radio on there phone, while everyone else is using two...another huge factor in battery savings. Pretty amazing i am getting about 50% battery life than any android phone, with about 1/3 less battery size.
- Camera the best out of all the phones i have tried, same with video
- Ipod, nuff said
Cons - Screen size, You cannot even tell they upped the screen size. Everything looks exactly the same when web browsing since they did not increase the width. Videos do not look anywhere near as good as the Gnex or SIII i used. Whenever you go on youtube with the iphone and go to a HD video it just looks like crap, letter boxed, and just looks like its running at 480p. However the video you take with the phone looks great and HD. I am still searching for HD video on youtube that will look great on it. I think because of the aspect ratio it does not display good, videos are going to have to be tailored to it to show correct/HD. Its amazing when you show people the new iphone 5 not one person has noticed the screen is bigger lol. Almost disappointing in a way
- iOS - Getting stale after 5yrs of using it, i was tired of it two years ago and I am dying to find a new phone to replace iphones(HTC 8x is on my list, i love the new windows phone 8 OS)
S3 - Pros - Screen Size, options in the settings menu's.
Price - You could probably pick one up in like new condition, or new for $275-$400 easily on craigslist/full price no contract. Back in september when i bought mine there were a ton for $300-$375. If you have an upgrade availabe and decide to go with the S3, then buy the iphone 5 on contract upgrade for $200, Sell it for $500 on craigslist, buy a S3 for $300 and make $200 back...new phone = FREE
Camera - Good but not great, i would say its 75% of what the i5 is. The multi-burst feature is awesome though
Along with all the other camera options.
Cons - AMOLED blows outside
Battery Life - Good but not great
Colors non realistic and color profile cannot be changed unless you are
on the international version