Download Xcode from developer site vs install from app store I signed up for the (free) Apple Developer ID and downloaded the latest Xcode release from here. Is it any different from the App Store download/installation? If it's the same, why does the App Store keep asking me about billing information (credit card and other details) every time I try to use the App Store to install Xcode?

Is there any difference between the two? I.e., download from developer.apple.com with Developer ID vs signing into the App Store with an Apple ID and subsequently giving your billing information?

Small note: The App Store info page puts the Xcode 4.4.1 app size at 1.46GB while the Apple Developer site puts the Xcode 4.4.1 dmg file at 1.81GB. The difference in size caught my attention and I wonder if they are two different things (new to the Mac). Plus I would rather use some sort of download accelerator (DTA on my Firefox will do just fine) in order to download this monstrous thing!
As far as I can tell, they are the same. The size difference might be due to additional files Xcode from the App Store doesn't download by default, that Xcode from the site might have. 

I have Xcode from the App Store; the first time I opened it it asked to download the Mobile Device Framework to proceed.

I suppose this must come bundled with Xcode from the website. It wouldn't surprise me if it were, as this framework seems to be needed before Xcode can start. I suppose Apple distributes its MAS Xcode with users with stable internet connections and single-install in mind, while the website version for users who might want to deploy it to several machines, in which case it would be a drag to have to download any extra-crucial elements that don't come with the installer package. 

Why wouldn't Apple just put everything that is needed on the MAS installer? Probably an issue with permissions; MAS applications aren't supposed to ask for your password to install. These Xcode components, installed later through the app, might touch delicate areas of the system which the MAS installer has no access to.

My suggestion: If you plan on using a download assistant/accelerator and have trouble with your billing for the MAS I suggest you download from the website.  I doubt there is any difference at all regarding the app itself.

PS: If you do, maybe come back and comment if you had to download any additional components or if it was a full installation straight out of the disk image, as to increase the knowledge of the community for any further reference.