Re: Sizes
I'll bet drivers are a rounding error in the size of Android installs. There isn't REALLY that much variation in Android phones, since there are only about a half dozen SoC vendors, and not too many parts to choose from for stuff that's separate like wifi, bluetooth etc. Even Macs have far more variation, and PCs are probably 2-3 orders of magnitude more than Android.
An operating system doesn't get to be 3GB in size without a lot of media like wallpapers, sounds, localization strings, and so forth. The amount of actual instruction/code in binaries probably increases at a very slow rate.