The first 2 are phones, the last one is a tablet. If you don't know if you need a phone or a tablet, better buy nothing. Or do you mean an iPhone in stead of an iPad?

All phones are much cheaper when they are subsidised. Then the subscription to the phone company is more expensive. And it really depends on your planned use of the phone what's the cheapest option seen over the full 2-year such a subscription lasts.