get the one that says pc-engine on it. they're the niciestesest

LOLz i hear they have the best sound quality

hehehe...and here is how to DIY

thanks guys. very helpful. im leanin towards the dmg, because im most concerned with the sound quality. unless i can find maybe a gbp or gbc prosound modded.  but i'd need to get the dmg backlit...anyone know of a good place  or person that does that?
and RE VBA: is there another emulator i should use instead to record from emulator?

If you don't use the wave for samples(drum kits etc), SP is another option to consider, as arottenbit said. Doesn't have the best sound, but, it is compatible with all types of cartridges, has a light and colours, it is small and foldable (screen stays clean) and sounds good enough for sure...

You can also add a mini-jack audio output as Capcomposer shows here.
It's also possible to fit the mini-jack on the left of the cart-slot so that you can save the link port for syncing the SP.
NeX has also shown a way on how to improve the sound.

EDIT: that was for getting only one. If you plan to get more than one, it's a different story

i have a joke about the term Handheld now

Go with the original.

Power mod a GBP to remove noise and you're all set. Small, light, looks fabulous with or without a backlight, and with a li-poly mod the batteries will last a good while and you won't get nasty noises from your LSDJ cartridge overloading the power supply (with AAAs you will.)

wave channel emulation on vba sucks. Dont worry about that.

In case you're not making any mod on your gameboy i would recomend you a GBA SP for lives (it has a nice backlit), a dmg for recordings and a GB Light for composing (nice display and confortable to use).

The dmg has the best output quality.
..but if you are going to make a prosound mod, they are kinda all the same..

I still prefer the dmg just for its design.. but gbc and gba are much more powerfull!!

http://www.herbertweixelbaum.com/comparison.htm

That might help you

I say go with the DMG

so i've been experimenting with lsdj and now that ive got the hang of it i must say i enjoy it. i've been using my psp and emulators just to experiment for now and see if i like it before i wasted my money. now that i'm looking to purchase a gameboy and cart, my questions is which gameboy model should i go with? it seems the weapon of choice is the dmg. from what i understand the sound quality is best on the original model? what about say a gbc with a pro sound mod? does pro sound improve the sound quality on the dmg?
also on a slightly unrelated topic. when i take my songs off my psp and run them on in visual boy advance to record, some of my instruments sound screwed up - mainly my pulse kick sounds phased out and my wav channel vol is incredibly low. is this normal? Thanks!