Which is better, 15% or 5% niacinamide concentration?

I've been using a 15% niacinamide product lately. As I used it, a question suddenly popped into my head, so I'm posting this.

I have been using niacinamide consistently because I heard it is good for skin tone, blemishes, pores, and texture, but I noticed in an article that opinions regarding the concentration are really diverse.

Some people say that you need to use a high-concentration product of about 10–15% to definitely feel the effects, while others say that 5% is sufficient and that high concentrations can actually irritate the skin, so I became curious about what is correct.

I am currently using the 15% product, but honestly, I'm not sure how different the effects are compared to the 5% product. I have sensitive skin with atopic dermatitis, but I don't really feel any irritation. I'm also wondering if it's better because it's higher concentration, or if it's more important to use it consistently at an appropriate concentration.

Has anyone tried using niacinamide at various concentrations? For those who have personally used 5% and 10–15%, I am curious if you actually felt a difference in effectiveness.

I just bought and have been using the 15% concentration without much thought, assuming a higher concentration would be better. However, seeing opinions saying otherwise has made me a little worried. Haha. I'm curious if anyone else uses niacin to know what concentration you were most satisfied with. :)