Rundown:
melonDS is brought up on the updates on the Discord of TASVideos ever since v0.1.
Arisotura made this as a spite emulator against DeSmuME.
All features and emulation work is to avoid using hacky methods.
The emulator is more accurate than DeSmuME (besides endrift's medusa which is in preivew for 2 years and is the next emulator goal).
It's also able to draw the ground better than DeSmuME rather than having broken pixels all over the place. (there will be images in a bit)
It supports Wifi before DeSmuME and it's much cleaner (in which the response from DeSmuME was to
work and then release theirs)
When melonDS first came out it was noted that DeSmuME was playing catchup on certain functionality.
There is DSi work being done to the emulator so something besides no$ will support that system.
Between versions 0.7.1 and 0.7.2 there was a massive timing renovation that made some games bug out, however it's been fixed for the most part.
Test whatever game you enjoy and see how far it goes. If it's completable great.
If you land in a bug
make a report about it. It'll be looked after, and completed rather than deleted.