Maybe the newer ones - I have one of the older sega Radica ones, and it's not emulated at all. The newer handheld ones, though... awful sound emulation! The PSG is about half an octave lower than intended. Unacceptable.
This seems to be a pattern with these Sega handhelds. Is there a problem with the soldering or something? I'm sure someone would have noticed by now.
They probably noticed and don't give a damn. If I had that 'It prints money!' gif with a Sega handheld instead of a DS lite, I'd surely be posting it in response.