Haki. I really like "hidden badass" tropes, like in HxH almost everyone has ten, but unless you unleash your bloodlust aura, you may hide and go unnoticed. Sure, it requires training, but the outcome is great.
Having big black wings and fire all the time is like screaming for trouble, also, while with training you can develop and change your haki, lunarian genes are just there, next chapter Luffy will trash those seraphims with his G5 Nika powers, and prove them pointless.
The only thing I really like in lunarian approach is that you don't need to train, you already have everything there for you.