Keratin smoothing is a temporary process which does not alter the structure or damage the hair. It lasts 3-5 months & is suitable to calm bulk & frizz without disturbing natural curl or wave. It is considered as a deep protein treatment & improves the quality of your hair.
Permanent straightening (no ammonia) is suitable for stronger, unmanageable hair. With that in mind, being no ammonia it is still considered the safest and less damaging and effective.