As sndpalce showed, overall, Sprint works out to be cheaper. I went from a $110 bill on VZW w/ 3g to $80 w/ Sprint when I got my Epic almost 2 years ago.
However, I'm still a bit annoyed at the 'Premium Data' charge. As an IT professional, data to me is a series of 0's and 1's. My data usage is measured in how many of these 0's and 1's I use. When roaming, I don't get charged seperately for 'data' and 'premium data'. So, what's 'Premium Data'? Sprint can't define it, and they can't quantify it by itemizing it on my bill, but for the past 2 years, I've been paying for it. I still don't have 4G coverage at my home in a suburb of NYC (and my phone rarely switches to 4G even when I'm in the 4G coverage areas), and there's no data my Epic can access that other non-4G smartphones can't, so Premium Data is 'not' 4G, right?
If they want to call it a 'Smartphone' fee or 'Unlimited Data Fee', fine...whatever. Actually, I'd just as soon they increase the data plan fees and be done with it. Just stop the marketing BS.
You don't get "premium data" when roaming on Verizon if you are a Sprint customer.