AT&T powers up its blazing new 4G LTE network in Beantown, but does it measure up to Verizon? We jump in the car with a bunch of phones to find out.

BOSTON—It's still nowhere near the size of Verizon's, but slowly but surely, AT&T is ramping up its 4G LTE network. Today, it flipped the LTE switch on four more cities: Boston, Washington D.C., Baltimore, and Athens, Georgia. That brings AT&T's total number of LTE markets to nine, including Atlanta, Chicago, Houston, San Antonio, and Dallas Fort-Worth.

Since I live in northeastern Massachusetts, I hit the road to run some tests in downtown Boston, Cambridge, and Brookline. I also stopped by West Newton, about five miles west of the city border, to see how far it extended. For this test, AT&T sent us two brand new phones: the . Both have a nifty little 4G LTE icon that lights up whenever you're in the right coverage area. For comparison purposes, I also brought along a , which supports AT&T's older HSPA+ 21 protocol, and the , which works on Verizon's LTE network.

First, let's get the big news out of the way: AT&T's LTE network is fast. With the right conditions, it's as speedy as Verizon's LTE network, or even faster, as we had found in . I saw speeds in excess of 25 Mbps down, in fact. But it's not terribly consistent yet, at least in direct comparison to Verizon—and not unlike what we found in our nationwide test earlier this year.

For example, in Cambridge ("A" on the map, above left) and downtown Boston ("B"), I saw easily repeatable 25 Mbps+ results on Verizon, but AT&T results hovered in the 15 Mbps to 16 Mbps range—which is still extremely fast for a cellular data connection. In Brookline ("C"), AT&T took the lead, with results surpassing 25 Mbps, whereas Verizon LTE fell to about 10 Mbps down in my test location. Once I drove out to West Newton ("D"), LTE performance degraded on both Verizon and AT&T, at least to the point where it was now equivalent to a fast HSPA+ conncetion (in the 8 Mbps to 10 Mbps range).

At first, I had trouble achieving LTE-like speeds with the HTC Vivid, but it turned out AT&T didn't provision its SIM card correctly. I confirmed this by swapping the SIM cards; once I did that, the Vivid hit LTE consistently, and the Skyrocket stopped connecting to it, showing only "4G" instead (like other HSPA+ phones on AT&T). Once I learned this, I doubled back and redid my Cambridge results, just to make sure both phones pulled down the same numbers on AT&T 4G LTE (they did).

Reception Quality Is Important

That said, the handset itself has a lot to do with the equation. When you put the Skyrocket next to the Vivid, it's clear the Skyrocket is both thinner and lighter; in fact, it looks just as thin as an original 3G Galaxy S. Considering the new model contains LTE support, it's a pretty amazing feat of engineering—that is, until you try and use it. Unfortunately, Samsung sacrificed reception quality to get the Galaxy S II Skyrocket so thin. Several times during the test, the Skyrocket latched onto 4G LTE, but then failed to deliver data. That's despite waiting over a minute, and after a reboot to double-check. The HTC Vivid, on the other hand, performed much more consistently in the same locations that had given the Skyrocket trouble. This is why we test reception so heavily in each and every one of our reviews, incidentally.

Another surprise: the Atrix 2, with its HSPA+ 21 radio, delivered results all over the board, from a low of 2100 Kbps down (roughly equal to HSPA 7.2 on a good day), to a very fast 13 Mbps down (which is squarely in LTE territory, if on the low end).

I'm glad I had both LTE phones for this test, because if AT&T had just sent me the Skyrocket (and with the good SIM), I would have ended up thinking AT&T's LTE network was spotty and inconsistent. Instead, I can report that while AT&T LTE doesn't extend quite as far as Verizon LTE in Boston, and doesn't always reach the same speeds, it's capable of the same blistering performance with the right conditions. All told, not bad for a launch day.

If any of this interests you, AT&T 4G LTE customers can get 200MB for $15 per month, and an additional $15 for another 200MB with DataPlus. AT&T's DataPro plan offers 2GB for $25 per month, plus $10 per gigabyte afterwards. You can also use your phone as a mobile LTE hotspot for $45 per month; that plan comes with 4GB of data.

In the meantime, look for full reviews of the Skyrocket and the Vivid soon.

Update 11/09/11: After more testing, we eventually traced the Skyrocket's reception issues to a faulty SIM card (even when provisioned correctly). Samsung sent us a second Skyrocket, which performed similarly to the HTC Vivid on a new round of LTE speed tests.

For more from Jamie, follow him on Twitter: @jlendino.