My bag progression went from mam to nikki to matinee... and personally they all work for me but in different ways. The mam is a great classy bag that holds a ton but still has that slouch. The nikki is a great hold everything bag, and again has the slouch we all crave. I do feel like the nikki is more casual/boho and doesn't work with some outfits. I just got my mattie last week. At first I thought it was too big, but then fell in love with it. The trick is when you wear it on your shoulder to wear it slightly behind you, or else it looks to bulky IMO. I have also tried on the noir mini nikki, and think that would be a great everyday bag if you don't carry much more than a wallet, makeup bag, phone, and keys. I plan on snagging one of those at the SS if I can.
Basically RM rocks, and all of her bags are amazing. I've never tried on the MAB, but from looking at it at Saks, it looked huge! (but that was when it was stuffed so who knows)
oops... I'm 5'6'' and 130 lbs