Is the 3G network used by the iPad the same as the 4G network used by the iPhone? Both my iPhone 4S and iPad 2 are running iOS 5.1. Both are AT&amp;T models. When not connected to Wi-Fi, the network indicator on the iPhone shows 4G while the iPad shows 3G. Does the iPad use a different network? 

I'm not looking to stir up religious fervor over the semantics of 4G vs. 4G LTE. I'm just trying to find out if my iPad and my iPhone have the same data connection capabilities or not.
iPhone 4S supports HSPA+, while iPad 2 doesn't.

HSPA+ is technically not 4G, but is being advertised as 4G by networks like AT&amp;T and T-Mobile in US. Pre-iOS 5.1, Apple wasn't calling HSPA+ a 4G network, but they have started calling it 4G now to match AT&amp;T's other "4G" phones that are using the same signals and protocols as the iPhone.

If you are in HSPA+ supported area, you should hopefully get better speeds on iPhone 4S.