From my knowledge (and please someone correct me if I'm wrong) but dermabrasion and chemical peels are both forms of deep exfoliation by removing the top layers of skin, eliminating dead skin cells. This could really eliminate a lot of debris and clear out the pores, which would help acne, theoretically.
I think ProActiv is salicylic acid which helps tremendously with acne by drying out the pimples.
I have issues with blackheads too and though I can get rid of some myself, the best (and really only effective way I know) way to get of them is the extractions part during a facial.
If you want to get rid of acne use this:
http://www.amazon.com/ANSR-Beam-Char.../dp/B0030ZRQQ8
The blue light kills the bacteria instead of drying out the blemish in which the bacteria will be back in a week.
In terms of which you should pick, I would ask a professional to make a suggestion based on your skin type, aka your friend.
I'm NOT an esthetician, so if anything I've said is incorrect, please let me know.