I have not seen it yet, but Carrie is KNOWN for her odd style. She mixes high couture with vintage finds and often sports low brow attire with a girly twist. With her hair and body she can generally carry it off, but even then, sometimes her outfits are uber-bizarre. Her personality is that she enjoys blurring boundaries with her costuming.
Samantha is a power-dresser, whether it's for work or going out. Her clothes are never subtle but always sexy.
Charlotte dresses in classic clothing that always compliments her figure. Sometimes they are clean, neat black dresses and sometimes preppy Ralph Lauren-esque pieces, which suits her upper crust wasp, slightly conservative upbringing. I did notice that when she converted her attire modified a bit.

Miranda is the one who's style changed the most. Hers started out in manly, angular suits to compliment her law career and no nonsense personality...over time she seemed to loosen up and be less afraid to try on some more feminine looks. Still not outwardly sexy, for the most part, but less mannish. In the previews for the movie she seems to have embraced her girlyness, but I will have to see.