"Get two plastic surgeons in a room, you'll have three opinions."
Each surgeon has a different opinion on bra use following breast surgery. As long as the garment is not painful, ill-fitting or irritating to the healing incision, there is no wrong answer.
Following breast surgery of any kind, I place a sterile surgical bra in the operating room that remains in place for the first 48 hours. This prevents unsterile garments from entering the operating room, and may therefore decrease the incidence of infection. After 48 hours, I recommended that a soft cotton sports bra be used for the following month. I prefer a sports bra because it is comfortable yet supportive, and prevents excess breast weight from resting on the fresh incisions. The sports bra is also used to support breast implants from the same process following breast augmentation.
Some physicians specifically use an underwire bra to help "set the fold" under the breast following breast surgery. My opinion is that this anatomical landmark is set in the operating room, and can not be effectively changed through external pressure. I also feel that the wire can apply undue pressure on the healing incisions.
Conversely, other physicians use a bandeau or breast strap placed on the upper portion of the chest following breast augmentation. This is used to apply pressure to the top of the breast implant and help to drop the implant into a more ideal location.
In general, if a garment is tight and painful, it can harm the blood flow to the breast and potentially cause adverse results. Another old adage in plastic surgery: "never ruin a good operation with a bad dressing." Accordingly, I recommend a soft, comfortably fitting sports bra for the first month following surgery.