Is it worth lossing the unlimited data for Verizon?

I currently have a iPhone 4 from Verizon with unlimited 3G which is good but it's slow I've been looking to getting the 5 with a 4gb of mobile data is it worth lossing the unlimited 3G? Also I have the upgrade in my line but if I upgrade my line I will Lose it ether way.

I will be switching to T- mobile and get unlimited

Well, you can keep unlimited a couple ways and still upgrade. You can just pay full price for the new phone and stay month to month. But you may not want to pay $600-$700 for new phone.

There's a way you can get the 2-year contract price on an upgrade and still keep unlimited data, but it's kind of tricky. And it requires that you have another line (or pay for another line) on your plan that doesn't have data. Instructions at the link below.

http://forums.imore.com/carrier-discussion-lounge/253970-how-keep-unlimited-data-verizon-get-subsidized-phone-if-you-have-family-plan.html

I've found that cell phone data tends to be constantly switching around from 4g to 2g to Wi-Fi to GPRS.So, any plan will give you quick 4g as long as you find a good spot and stay still. The question is: do you want to pay full retail on the phone for that luxury? Just pay the lump sum once and forget about it. Then you'll have the luxury of being able to choose a cheap plan with no contract.