well. in reality if we're talking just straight square/triangle waves/ noise.. then yes software vs... well... software/hardware will sound ultimately the same minus a bit of noise floor and stability. It's all code anyways right? Unless we're talking SID's... in which case analog filters are used.

And in the end... it's what you do with those waveforms and noise channels that really matters.

'Cuz we all know emulators sound exactly the same, amirite? XD

EDIT: as for building portAtaris, even with original hardware it's not too hard. If you're curious you may want to check out Ben Heckendorn's site: benheck.com

Ben probably didn't invent the idea of turning regular consoles into portable game consoles, but he's certainly been very prolific and has been doing it for a long time. His first was an Atari 2600. You'll find lots of ideas, how-to instructions, and inane (but fun) chatter on his website and forums.

Or you can use an Atari 2600 emulator on your modern handheld console of choice.

Um, yes. This has been around for ages. And even if you don't use a flashback, the atari's mainboard is like less than 4 inches square if you cut it down.

http://www.atarimuseum.com/fb2hacks/page1.htm

The guy who built that builds all kinds of consoles into hand helds.
Infact theres a whole scene of guys who turn n64s and other stuff into handhelds.

you can modify the flashbacks to take carts...

I know the video says Atari Flashback, but if you watch, it can actually take game cartridges too. No midi at the moment.