I find that odd. I have a Copperhead (the blue one) and it is hands-down THE most buggiest mouse I have ever laid a finger on.
Refused to work in OSX, kept dropping out in Windows and caused the ZBoard drivers to fail to install if it was plugged in.......all these seemed to be known issues as well. The only problem that ever got resolved was OSX compatibility and that only came in the very latest firmware (6.18, a recent release) that was released over a year after the mouse came out.
Then I got a Habu......and it works flawlessly, having none of the issues above.
So, really not sure how you can say the internals are the same, my experiences show otherwise.