Looking at the coverage map I can tell you the site density is not as high as it needs to be.
iPhone 4 on AT&T:
I live in Phoenix and I'm on straight talk with the ATT sim. We have only 1900 here as far as I'm aware and I get pretty good indoor coverage anywhere I go. The only times I have lower signal is in the middle of old buildings make from blocks as thick as a fridge.
At home, my office, offices I go to train, and friend's homes, I'm always sitting at 3 or more bars. Although I do have a moto phone which I think hold pretty good signal, compared to other phone makers.
Even AT&T does quality control checks on their handsets and they aren't going to release that many crappy handsets, especially with the Skyrocket being one of their most popular handsets. The Skyrocket actually gets better reception than a lot of their current phones.
http://www.isu.edu (Idaho State University)
Another huge mistake that they made when they were rolling out 3G on PCS, and that they make again with AWS LTE and CLR UMTS is that they wouldn't allow you to shut 3G off on those devices, and they seemed intent on holding on to 3G until there were no bars left, instead of switching to the much better 850mhz GSM/EDGE network. You should always be allowed to choose what network you're using, and I find it appalling that even the iPhone 4s can't choose (unless it's JB'ed like mine). I have had several times where it chose the wrong network if I was near an EDGE tower, but there was a UMTS tower a few miles away. I'd rather have 5 bars of EDGE than none of UMTS any day!
I usually support government regulation, but It is unfortunate that the government over-regulated and killed the AT&T/ T-Mobile Merger
The best explanation of the pricing nutiness in the industry.
Why Sprint and T-Mo will always suck.
The only way to end the pricing insanity is to eliminate contracts and subsidies.
I want Wifi calling on AT&T.
If you text while driving, you're an idiot. End of story.
That said, if the surroundings are reasonably flat, a suburban PCS cell can easily reach 3-4 miles and still have some indoor coverage. Outdoors, that distance can be much farther, but is obviously highly dependent on terrain. With an external antenna and amplifier, 10-15 miles is doable on PCS.
AT&T and T-Mobile use GSM technology whereas Sprint and Verizon use CDMA. The difference in building penetration is due to two factors. One, the fact that GSM doesn't penetrate buildings as well as CDMA. And second, antenna placement and design, which varies from phone to phone. Some phones like the HTC's put their antennas in the rear cover and have horrible reception. Motorola has a superior antenna that is based on their military devices and they generally get the best reception. The new iPhone 4S does very well too as it employs two separate antennas. But, the iPhone 4, 3G and 3GS all have reception problems.
The difference between the two phones could simply be due to the different antenna designs or it could be a GSM/CDMA thing.
It has NOTHING to do with the air interface. It's all about FREQUENCY. Lower frequencies penetrate objects (read: buildings) better than higher frequencies. CDMA running on 1900 is no better than GSM on 1900. Same with 850.
Not trying to single you out, this myth is repeated fairly often here and on a lot of other forums/discussion boards.