I am a bridesmaid for two weddings this year. One bride went with David's Bridal, the other with Azazie. Similar colors, different dresses. Anyway, I measured an 8 for both dresses.
My body type is athletic. I lift weights, but I am not to body builder standards whatsoever. I measured perfectly at an 8 for Azazie.
David's Bridal Dress: slightly tight in bust area when I wear a bra, more expensive, a bit uncomfortable. (I do weight lift, so thought it was that).
Azazie: Comfortable, slight bigger, no bra necessary!!! Still fits well, just not as tight as I normally wear dresses. Love the pockets!
If I were a bride, go with the cheaper dresses that people can shorten and actually wear again. I can wear the Azazie Natalie dress shortened with a blazer to work. Being a bridesmaid is already pretty expensive, so find something cute and inexpensive. The David's Bridal dress (one shoulder with a slit) is something I can't see myself wearing again.