I personally believe iPhone users would like to consume data at the same rate (or higher) than us Droiders, but they do have less coverage, AND more capacity issues which no doubt keep their numbers lower.
No flash, either.
Becomes a potentially interesting marketing point. If you can point to 25-50% more data (it will increase when Froyo gives everyone flash, and then with LTE), you can ask the question if the IPhone is so much better, then why do android users utilize their phone's capability so much more?