I wouldn't use any other type. I used to use Affirm mild when I was relaxed years ago and my hair was the best it ever was. With a mild relaxer the hair breaks down slower and I find that I don't burn as easily if ever.
I just relaxed on Sat. after being natural for almost 3yrs and I used a Mizani mild and MY HAIR LOOKS GREAT!!! When I was shampooed, I could still see some curls as opposed to limp hair and it is straight when set. Mild relaxers DO work on 4a/4b hair. Believe me, I know. I plan to post pictures when I have had a few touch-ups.