I'm an iPhone man mate, they're simple to use and the app store is regarded as the very best in the world. I'm not really keen on Android phones but that's simply because I have an iPhone.
The only thing about Apple is that it's slightly limited, the main thing is that you can't use Flash Player so are basically limited to youtube if you want to watch videos, although some sites are Apple compatible, I've learnt to live with this and it's really not as bad as some people make it out to be.
The operating systems are basically Windows vs Mac, the classic debate, one is good for some things, one is good for the other.
If I was going for one I would go for the iPhone 4, it will be considerably cheaper than the new 4S (Which is a glorified 4) and should have everything you're looking for. An android phone will be cheaper and you might get more freebies as part of the deal, unfortunately Apple are at a position in the market atm that they can charge what they like and not offer any iincentives and people will still buy their product so they are in a good place.
One of the main advantages of Apple though is that the customer service is second to none, they are very good at replacing faulty units (Very rare occurence) without making a big song and dance about it.
Signal can sometimes be a bit of an issue with iPhones and the battery life is basically limited to about a day through normal use, Facebook is the biggest killer of mine, too easy to be on it all day. I'm not sure if Android phones are the same but it will probably depend on what model you're after.
Insurance companies tend to have a higher excess on iPhones if they are lost or stolen too.
Hope this helps mate this is basically everything I know. On paper with the benefits and the cost of everything Android's are better but I have an iPhone, love it and don't mind this, a LOT of others are the same.