Fraxel Vs ProFractional for Acne Scarring?

I had 1 treatment of Fraxel laser at medium strength last spring for acne scarring. I knew at the time I would require more than one treatment but immediately following I moved from the area.

Yesterday, I had a dermatologist suggest ProFractional to me and again was told I would need at least two treatments,most likely three. I was told it would be painless,as opposed to the Fraxel that I found to be pretty painful during the procedure (not afterwards). I have never heard of this and wondered what the difference between the two are and if it's normal to request a sedative.