I've recently started to collect these, and with these I mean, NES Classics on Game Boy Advance. I've been checking out wikipedia and read about the the different versions.

http://en.wikipedia.org/wiki/Classic_NES_Series

Now for the questions, is there any differences to the US and EUR releases? I've been comparing NES Classic Metroid to the original PAL version of NES Metroid, and found out that the GBA version must be in 60 hz. The music is not exactly the same, and the speed on GBA is much faster.

Metroid on Famicom Disk System allowed you to save (?) and does the Japan version on GBA let you do the same? I think the Disk System version had some extra sounds too, does the GBA version emulate the Disksystem sounds?

My girlfriend let me borrow her GBA SP and I've been playing Super Mario 1 on it.  I don't know about the Hertz and stuff like that, but it is definitely not exactly the same.  Mario jumps a bit farther.  It's annoying because when you've played it a million times on NES you know where to jump and how to jump and how to press the button, but on the GBA version it is off.