Both are great phones.
The build quality on the Apple is far superior than the Samsung, which is kinda important seeing as we are all forced to get 2 years agreements now.
There are more features on the Samsung but many of them require another Samsung to work with.
Depends what you want really.
If you want full control over your phone and lots of techy bits go Samsung. ( Although there is currently an exploit out, where someone can text you a link that wipes your phone ha )
If you are going to be running Windows 8 at home and at work, I would look to using a Windows based phone as the integration is going to be amazing.
If you want a phone that is going to last and do everything you want it to do well ( maybe not perfect as it has to be done the Apple way ) go Iphone.
I went Iphone 5, tried the Samsung wasn't swayed. And since my last iphone 4 lasted over 2 and a half years, travelled the world, was used as an Ipod to snowboard with so has seen all extremes of weather. I am happy with my choice.
I am not an Apple fan boy.. I hate Ipads and all that they stand for! Piece of crap, limited wastes of cash!
I recently won an Ipad through work and gave it to my girlfriend that same night.. She is a techy retard and loves it.. pretty much sums them up tbh.