I am a 4a/b all natural (no texlax, no relax, no tex.etc.) I used the maxiglide once and my hair was frizzy at the ends, it didnt straighten my ends properly. I returned it and purchased the FHI and it works wonders on my hair! I will admit a girlfriend on mine purchased the CHI and I used it on the front on my hair which is 4a and my it straightened really nice and silky however, I didn't use the CHI on the middle/lower back of my hair which is a tight 4b.
Lastly, I believe you should use VERY small/ thin pieces of hair when flat ironing inorder to straighten it smooth from roots to ends, especially in the tightly coiled areas. Now, that I have the FHI, I need to locate a GREAT heat protector!