Apple and/or Sprint experience only!?

[JES27]

So i am in a bit of confusion. I currently have a Blackberry Tour from Sprint. I am eligible for a $150.00 upgrade and Im not sure which phone to buy. It is between the iPhone 4S with 16gigabytes, the iPhone 4 with 8gigabytes OR the Motorola Photon. I've looked up reviews for all three and I still do not know which one to get. The Photon looks kind of complicated but I want a phone that is going to last me a while and doesn't have crappy battery life. So far I know there isn't a major difference between the two iPhones except the Siri app and that the iPhone 4S is a little bit quicker. However, the only thing stopping me from buying the iPhone is that I have to purchase insurance through Apple. This confuses me and I need someone to explain it to me. So if i have an iPhone, and it is defected or it breaks.. do I have to go to Apple or can I go to my phone carrier (Sprint).. Also, if I don't purchase the insurance, does that mean I have to payevery timee something is wrong with my phone and I need it replaced?? Please help!