The "best" decompiler depends on your budget and technical goals. Most modern workflows involve a combination of the following:
Tracking register states to determine function arguments and return values. nds decompiler
It ensures that even if the original hardware fails, the logic and "soul" of the game are preserved in a format that can be understood by future generations of programmers. The "best" decompiler depends on your budget and
for free NDS reverse engineering. Use IDA Pro + Hex-Rays only if you do NDS RE professionally. nds decompiler
Developed by the NSA, Ghidra is currently the gold standard for hobbyist NDS reverse engineering.