My take on the moms of the show:
Kelly was by far my favorite mom - she came off as the least selfish and internally competitive of the bunch and that's why I liked her so much - her kids were there to dance and do their best and it wasn't about beating or being better than other people to her like it is w/ so many of the others. And considering how talented her kids were, especially Brooke, that is very admirable (and rare).
IMO Christi was driven almost entirely by the competition between her daughter and Maddie in the quest to be the number one dancer in the junior age group at that specific studio - yes she was nice to others, but I don't think that would have been the case as much had they been true "competition" for Chloe (cause none of them really are/were, only Maddie was/is, cause Brooke is just too much older).
Melissa is just the complete epitomie of a kiss-up, do whatever it takes to get my kid ahead no matter what the cost "dance mom". She would befriend, sleep with, pay off, etc., whoever she needed to in order to get what she wants for her kids. And she is very good at this and was thus kicking Christi's butt in their little contest to have their kid be the "favorite" or the "best". When the show started the two girls were almost equals, but by the end Maddie was clearly very far ahead of Chloe, especially in Abby's eyes.
Holly to me was/is more of a wannabee dance mom who was just kind of there, but not really a player in the big scheme of things. Her daughter was never any real threat talent-wise to the others and was mostly the designated back up dancer/supporting role. That she quit a good job for this garbage show was really disappointing and not very bright IMO. Holly really wasn't as deeply involved or significant in the politics of the studio, cause her daughter wasn't a top dancer - if Nia left and went to another studio, what really would have been the impact to the team? That wasn't the case w/ the others who all brought some form of special skill or ability to the mix - unless you want to count Nia's death drop move ;), but that one move hardly compares to the stuff the others can do (and I'm sure it could be taught to McKenzie quickly if they really needed it).
I feel bad for Chloe and Maddie because those two girls are going to be competiting against each other for the rest of their lives - the public will have "where are they nows" comparing their careers, their relationships, their looks, etc. It will never end - even when they are 80 years old people will still be comparing them (kind of like the Jennifer Aniston, Angelina Jolie situation). And for this they can thank their mothers.