IPhone 5 vs iPad with Retina Display?

I have the chance to either get an iPhone 5 or the iPad with retina display at the end of this month. I was wondering where I could get it cheapest and which one I should choose.

As you are really set on these two I would say what is your need.
Do you need the most portable take the iPhone.
Do you want the best "computer" take the iPad.
What do you need it for, do you want to call with it? Take the iPhone, if you want to use it for reading, playing games or working take the iPad.
It just all depends on you. I'd make a list of the things I want in the device.

About the price the cheapest of course is with an internet subscription or something like that. If you want it without apple still has the "lowest" price, you won't find it brand new and cheaper.
If you really want cheaper you should look into second hand.