There may be something to this.
There is a little shop I like to shop at. The shop is inside a building with a metal roof. Now you would not expect to get a good signal in there. I don't.
I have go outside in the parking lot to make a phone call. A friend of mine's daughter whips out her Iphone one day and starts talking away while in this same store. I asked her who her carrier was. Att. She gets 3 bars in the store.
I researched it and there is only one Att Tower in that area. so we are both using the exact same tower and using the exact same carrier but her reception is so much better.
In general though I don't usually experience a problem with signal strength almost anywhere else I go. No dropped calls ever with the EVO 3D.