I'd go with the iPhone 5 personally, Kesa.
I got a S3 recently, and while I do like the thing, I've found the wifi on it to be erratic at best. Randomly loses authentication and passwords and randomly drops off my wireless networks, and it's not an operator error issue, lol. I find the Android settings mechanisms on the handset to be overly complex compared to the iPhone. GPS on my old iPhone was better as well. Apps selection is pretty comparable, but I find Android "free" apps to be so burdened with crapware and adverts they are often unusable. I find the iPhone "multitasking" superior to Android as well.
Having the Google ecosystem crammed down my face on the handset is a little unpleasant as well, but so is the iTunes/Apple walled garden ecosystem.
I've had a Galaxy Nexus for 6 months or so now. I've had mixed feelings about it so far, the negative being that it took until about 2 weeks ago before I got 4.0.2 (ICS) pushed out to me from 4.0.1. And it seemed like 4.0.1 probably had some bugs in it that should have been fixed a long long time ago, it was way too long to be stuck on it. The 4.0.2 update seemed to make my device less responsive. Then one week later I very surprisingly get 4.1.1 (Jelly Bean) or whatever finally pushed to me. It's a HUGE improvement over 4.0.x. My device is now incredibly snappy and smooth, and there are lots of usability improvements and new features. I'm now extremely satisfied with it.
I bought my wife a Galaxy S2 as it does everything she needs and it had dropped to $400 (from $600+) now that it wasn't the newest model. The TouchWiz stuff is a disaster, and the Kies thing is a disaster. However, I prefer the hardware of the S2 to my Galaxy Nexus. It's lighter, just the right size, and the camera takes better pictures (though it's slow).
Now that I know a bit more about all of this, what I'll probably do from now on when my current device has failed or got way too old is buy whatever Samsung model has been out for a year or so that is half the price of the latest one, and install my own ROM on it if need be to get rid of that TouchWiz crap. The hardware itself I think has gotten pretty much to a place where I am happy enough with it, as I just need something responsive, and with good camera/video. It's the software that is a real mess in droid land right now with all this TouchWiz add on crap. There's still a long way to go before Droid users can all get sensible software included out of the box.
I've done the iPhone/iPod thing before and never will again, completely turned off of Apple after living through that.
I still think the smartphone offerings are a bit of a cluster****, looking forward to the day when you can buy an open device that does what it should out of the box that you can get timely updates for and all the software works on it.