The advantage are the incremental builds they mention. If just one input file changes and you run ninja again, it'll only re-run one step instead of converting all files again.
I'm pretty sure make does that too. The problem is that most people don't know how to write a proper Makefile, even for a simple project, so make ends up doing more work than it should. For small projects, I've tried ninja a while ago, and frankly the effort seemed unjustified, since (a) I already could do the same things with make, and (b) make is already available on most unix-likes.
Ninja seems to be better suited for big projects, where make's slowness in dependency resolution shows. Ninja files also look easier to generate automatically.
Yes, Ninja files are very easy to generate, that’s it’s big selling point for me.
I have a project with dozens of C/C++/asm/precompiled libraries, a few thousand source files in all.
I would have trouble writing Makefile(s) for everything that would even be correct, let alone performant, either by hand or generated. But I have a set of Python scripts to generate a big Ninja build file and it all works very nicely.
