Well I remember when testing iOS 4, the final version was different in size than the beta; being bigger, and I did notice a couple of changes even though the build number was the same. But hey, believe what you want. All I'm saying is that things that need tweaking in the GM are fixed usually in the public release.
I've been beta testing software for 20 years, so yeah, I do know what I'm talking about.
To nitpick you said the iOS 4 beta was different sizes then the final. We are running the iOS 4.1 GM not a beta. It has already cleared beta and has been considered Gold Master so I really doubt we will see any changes. But in the grand scheme of things I guess anything is possible.