AT&T boasts of being "America's fastest 3G network", so I've been putting that claim to the test by comparing the speeds with Verizon and AT&T iPhones side-by-side. The results were incredibly surprising. To find out what they were, watch the video above then follow along after the break!

First of all, I must preface this by saying that these tests took place in Denver, CO. Testing elsewhere could yield significantly different results.

When it comes to numbers, AT&T typically (not always) has faster speeds as you can see in the screenshots above. However, when it came to real world tests with Safari and Facebook, Verizon was neck and neck with AT&T and often times faster.

When out and about, I was consistently getting these results, but not at home. In my house, I have very spotty AT&T coverage and typically connect to a microcell to ensure I can make a phone call. In order to test AT&T against Verizon, I unplugged the microcell and got surprisingly mixed results. Even though I often only have 1 or 2 bars with AT&T, browsing with the AT&T iPhone is usually significantly faster than with Verizon. I say usually, because there are times when AT&T slows down to match Verizon. It's very inconsistent to say the least.

I cannot emphasize enough how my results were obtained from Denver and cannot be generalized to all of America. In fact, Ally has been executing the same tests in the Chicago area and been getting significantly different results than me. Not only do the following screenshots show AT&T with must faster speeds, but Ally reports that the difference is undeniable in practice.

Now, Chicago is one of the best places to have AT&T because it is very stable and running HSPA 7.2. It just goes to show that location is very important when choosing a network. If possible, run tests yourself while within your return period before committing to a network. Here in Denver, I may be considering a switch to Verizon if the iPhone 5 is available on Verizon the same day as AT&T.

Your data speeds?

To help increase our sampling, please add your carrier, location, and current data speeds in comments. Lets see what iPhone 4 can do on Verizon and AT&T in different parts of the country!