To be fair, all emulators should be honored for working on many machines. while others brought some progress into the hacking scene or not, i think its all about the development. i chose MelonDS because of the frequent updates and maybe even good future WFC support, while download play over the internet might be a problem on its own but i wish it could be possible someday (or maybe it is and i am pretty outdated xd). Still, i had way better experience with MelonDS than others, but since every developer is using different plugins or emulation code, performance can vary on different machines (if im wrong on any information, im sorry xd). Which one is better depends probably on your machine and your preferred layout/features. Its not about competition i guess.