iOS vs Android. iOS is very structured, they set things the way they want. Android is more fluid, you set it the way you want. My son has an Apple 5, I have a Galaxy S III. When we are together, he tells me he wishes he was able to set his phone and do some of the things I do. But he is sort of stuck in an Apple environment...the tunes, a Mac, a pod, a tablet. Hard to switch. I on the other hand, have no Apple stuff, much more flexible.
And if you are interested in using your phone in the parks, be aware of the battery situation. I see phone battery threads every few weeks on the board here. The Apple people are always recommending various external chargers to bring to the parks and recharging the phones over some period of time. For me, I take two extra batteries (about the size of a credit card) and put in my pocket. If my battery runs low due to a lot of use in the park, I just pop in a new battery (10 seconds) and on my way. In normal, everyday use, I never need a spare battery, battery life is fantastic.
If you are close to buying, wait a bit until the S IV is announced. Get that, or an S III for a reduced amount if you find none of the new features and improvements to your liking or need.
In the end, personal preference, unless you were sort of stuck like my son.