I guess that the mods are closing your threads because there are already plenty of threads talking about the iPhone battery issues.
Now i do not think that your battery is bad at all since you are having/experiencing the same battery issue with 2 different iPhones.
One thing which can drop that fast your battery juice is a bad network signal on your phone, (Say you have 1 or 2 bars most of the time on your iphone) and in addition to that, there are apps running in the background which are trying and forcing to communicate with internet using your 3G since maybe you are not on wifi... and even if on wifi, they will eat some battery juice while running in the background. What about the brightness? turn off "Auto-Brightness" and set the bar to about 40%.
Location services, weather apps, email auto fetching, communication apps like Skype, Yahoo messenger etc... running in the background (the list is long) are sucking up your battery juices. Turn off most of those location services thing, turn off auto fetching emails if you do not need it. Completely close opened apps from the multitasking bar once you finish using them unless you know you will be using it soon again, apps like Skype i mean.
Calibrate your iPhone battery: let it drop till 2% or 1% (Don't let the phone die by shutting down automatically because it run out off battery juice) once you see it the battery reach 2% or 1% connect it to the electric cable, once you see it start charging, turn the phone off and leave it alone for about 6h or more (you can do that before go to bed) when you wake up in the morning do not remove the charger cable but turn on the iPhone and even if you see it 100% charged leave it alone for another 15 to 20mn or more if you can, after that unplug the charger and you have just calibrate your battery.
But a bad signal reception is not helping your battery no matter what you do or what iPhone you buy.
