Multimedia Linux

All those distros are ubuntu based. So just choose the one with the programs you are going to use.

You need to decide which software packages you want to use; if one of those has most/all the packages you want, go with those.

My personal preference is to start with a barebones install of a basic OS (I am a huge fan of Debian). Then you can install only what you want, and not have a bunch of crap that you'll never use. That's just my preference however.

That would kind of be hard since it don't have an internet connection.

Is their any way to find out what all programs each distro comes with so I can compare.

I'd guess they'd be on their websites?

You may also have problems with various codecs. Things like .mp4 encoding and flash can't ship with the distros. You'll need to remember to grab what codecs you need as well if they're not going to be bundled in.