My mom is due for her upgrade in a little less than a month and I thought I would take it from her (aren't I a good son...

Anyway, we both have Verizon and I see that they have recently released the iPhone 5. It costs $200 with a contract renewal. As I was browsing, I found that the iPhone 4 actually comes free with a contract renewal. I was wondering if I should fork over the $200 for the iPhone 5 or if I should just get the free phone. Are there any big differences that would convince me to buy the iPhone 5?
My phone is eligible for an upgrade in July. I am somewhat willing to wait that long but since I am an impatient person, I would rather use my mom's upgrade since she rarely uses her phone to begin with.
So, should I take the free iPhone 4 or buy the iPhone 5? Or, should I forget the two and wait until July for the upgrade for my phone?
Thanks for any help!