I don't have the Mia 3, so can't speak to that other than to say I believe it has 3 speeds. The Mia 2 (which is what I own and purchased for my DDs) has two speeds. I also think that the 2 (and probably the 3) is more watertight. I know there is a body brush head available for purchase, so you can take it in the shower. I haven't used it, though.
They are designed to remove makeup and skin oils 6x better than hands or a washcloth. I don't have acne and my DDs only have regular teenage stuff, so not really bad. I feel that it gets my skin cleaner and also allows the serums, lotions, etc. that I do use to be better absorbed. I really feel that my skin has improved in the almost year I have been using the Mia. I hope that by starting good skin cleansing habits early, my DDs will have better skin as they age. One DD is a competitive cheerleader so wears heavy competition makeup and the other is an actress and wears stage makeup.
I bought mine at Sephora during the Christmas season last year. It was not discounted, but included a full-size ($26) cleanser, a travel case, and some smaller product samples so I did get a "deal." I bought my DDs on sale from Nordstrom during the Anniversary Sale. Theirs do not have the product samples, but I think they would prefer to choose their own cleanser. I also got a replacement brush head and some clairisonic cleanser and lotion samples as a 500 pt reward at Sephora earlier this year. Clairisonic routinely sends me emails with discounts since I registered my Mia. Hope you enjoy yours if you decide to purchase one! Hope that info helps you! I'm sure that a salesperson at Sephora or Nordstrom could tell you more about them as well.
