woah, this caught my attention just now as i'm acutely aware of lameboy's shortcomings, but i haven't heard of gameyob -- so i gave it a whirl just now.
the good news is that sound reproduction indeed is way better on gameyob overall. i'd say it's currently about 85% of the way there in terms of accurate sound reproduction. whereas lameboy made WAV channel samples grainy and garbled beyond recognition, gameyob plays back samples MUCH clearer, i'd say on par with a GB color i guess.
the bad news is that is the noise channel still needs some tweaking. some of the noise instruments in the songs of mine that i tried out sounded a little too loud or "bright". although, the overall noise channel sounded quite good otherwise.
bottom line for OP: if you absolutely must get LSDJ on a DS form factor, gameyob is your best bet. although i'd question one's productivity with a DS lite anyhow, given the tiny and awkward start/select button placement... also, if you're going to emulate it at any rate, why not just do so with a better emulator on your computer?