On the off chance that you may have missed an advertisement or two in which carriers are bragging about their latest "3G" network speeds, this item might not be of particular interest. If you don't fall into that category, you might find the non-scientific study done by gadget blog Gizmodo of interest. In brief, here is what they found. In the tested cities, download speeds are in this graph:
And upload speeds are in this graph:
So, what does this mean to you? Well, first off, if you want a more symmetric connection, AT&T appears to be the best choice. For download speeds, on average, there isn't much difference between carriers. Finally, the results show that your results may vary depending on where you are. Helpful?