I'm planning on getting an iPhone 4 with a data plan, but now that they changed it... which do I choose?

Here's some background info on my internet use on phones: I go on YouTube moderately. I check Facebook constantly. I use Safari at LEAST twice a day. I get around a message or two on Mail a day. I download stuff from iTunes on my computer, rarely DL stuff onto my phone.

Does using apps like Weather and Stocks count?

Thanks a lot!!