I have blogged about how XT is way faster than Vodafone on several occasions. This particularity applies in areas outside of the major metro areas (since Vodafone drops to 2G there for the iPad, iPhone 3G and iPhone 3Gs).
Anyway, someone has done a nice wee video test of it and put it on YouTube.
I think the better part of each test is the real word usage with an App. The speed test is useful to show how much difference there is, but at the end of the day we use Apps in everyday life, not downloading 1meg test files
Black and White Version: As we knew, XT rocks on the iPad.