Both have pros and cons. Which is "best" depends on individual circumstance.
For me, thats currently IOS.
The hardware is without doubt very nice, and I don't have any real gripes with iOS.
The only thing that gets my goat is the restrictions Apple place on you with regards what you can do with the hardware that you have already paid for.
And Google and their partners don't? 
I'm talking about restrictions such as not being able to send a pic via Bluetooth, I really can see no valid reason for Apple to impose such draconian measures in trying to keep their garden locked down to that degree.
Presumably there's a reason why they can't differentiate between pics, and video with audio? Audio being the copyright issue, I guess? it would be daft to allow free transfer of audio with a product such is iTunes Store available, obviously. AirDrop works, but only to crApple devices.
What bothered me is the basic stuff, like creating a play list in the device. Its possible, but requires you to know the name of every track and create it visually from a list of tracks, rather than as thier played. Play a track >Oh I like that one>Add to favourites or create a new playlist>play another track>and so on. No, you have to remember the track name, go to playlist then find the name by adding from the playlist. Its arse backwards. Or, the finction is available, but only from one end, like sending a contact, you can't go to a conversation in texts and add a contact, you have to go to phone book, select contact, then sent it to the recipient.
iPhone is full of these one sided functions, in addition to the restrictions mentioned above.
Nokia never had any of that bollards. Everything was available, from both ends. But the brain forgets pain quite easily. I have to remind myself of the pain of constantly crashing and locking up Nokias, especially the n900, although that wasn't Symbian, which wasn't far behind on the crashing front either.