Compressed app (.ipa) larger in Xcode 4 than Xcode 3?

I recently switched to Xcode 4 (from Xcode 3), and noticed that the size of the compressed app files I'm generating jumped by > 3MB. I tried building it on Xcode 3 using the same project file as in Xcode 4, and there's still a size discrepa开发者_开发技巧ncy.

What should be my next step in debugging this? Are there particular Xcode settings or preferences I should check? How about project preferences that might be interpreted differently depending on the version of Xcode?

Maybe you are building a fat binary for two architectures.

Check the 'Architectures' option in the 'Build Settings' tab of you project. If it is set to 'Standard', Xcode will include binaries for both armv6 and armv7. Change it to 'Optimized', and Xcode will build for armv7 only. I think, Apple is using armv7 since the iPhone 3GS and 3rd generation iPod touch.