Hi,
I switched from an iPhone 4S to the iPhone 5 back in June. For my whole time with my 4S, I only needed a 2GB data plan. Ever since I switched to my 5, and use Verizon LTE, I've slowly creeped up to the 8GB/month data plan and may consider doing the final move to 10GB/month being that I KNOW, and won't allow myself to, go over that much data.
It seems that with LTE, I find myself streaming more live video (especially NFL Football with Verizon) because the bandwidth is so good.
I guess it's completely up to you though, I don't believe LTE takes up more data, I just believe that with the quality of the bandwith, you might find yourself using more of it. It's all about will power, which I have none of.
I hope that helps a bit.