Choosing between wider & flatter or narrower & higher implants for my profile: 5'6"/123lbs + 12" BWD

The difference between higher and lower profiles for a given volume is projection and for a given width is volume (with the high profile implant being greater in both scenarios). The moderate plus is the most commonly used profile in my practice. It allows for the most reasonable volume in a given BWD. In my practice, low profile implants are the least commonly used (widest and flattest). I will typically reserve high profile devices for smaller framed individuals or those seeking a less subtle more dramatic change (the opposite of natural). 
In general, the difference between a high and Mod (+), in reality, is very small (on the order of millimeters).  In my practice, I generally classify profile based upon patient preference. A higher profile provides a more dramatic look (size for size) vs. a moderate (+) profile which is relatively more subtle and understated. That being said the vast majority of patients will select a moderate + profile device (especially those seeking a more natural and subtle result).
I often find it is easier to decide on a profile (rather than a volume), this combined with BWD will determine volume. Trying to match a particular volume to a profile may lead a BWD mismatch. In my practice, smaller framed individuals do prefer higher profile devices. I discourage pursuing significant volume as this is a hallmark of the "augmented" or "fake" look. Small girls typically have smaller breasts. Over-sizing leads to a frame mismatch which is not "natural." The difference between mod (+) profile and high profile is subtle and less dramatic than the difference between low profile and the alternatives. Ultimately, it is a choice between more or less subtlety.
As always, discuss your concerns with a board certified plastic surgeon (ABPS).

Thank you for the question.
The difference between these implants have to do with the dimensions ( diameter and height) of the implants. For example, the high-profile implant has a greater projection and a smaller diameter compared to the moderate profile implant. The moderate plus profile implant as projection and diameter characteristics that fall between the moderate profile and high profile implants.
I prefer to have a wide selection of implants ( all profiles) available in the operating room. I use intraoperative sizers and place the patient in the upright position to evaluate breast size. Use of these sizers also allow me to select the breast implant profile (low, moderate, moderate plus, high-profile) that would most likely achieve the patient's goals. The patient's goal pictures are hanging on the wall, and allow for direct comparison.
I have found that this system is very helpful in improving the chances of achieving the patient's goals as consistently as possible. My best advice: more communication.
It is definitely worth spending more time (prior to the date of surgery) with your plastic surgeon to discuss further.  As you know, it will be important for many reasons, that you feel comfortable that you and your plastic surgeon are on the "same page" prior to proceeding.  Show your plastic surgeon what your goals using as many visual aids as possible.   This additional communication will go a  long way when it comes to helping alleviate your anxiety prior to proceeding.
I hope this helps.

Dear hellohelloyx,breast implant type and sizing selection is a complicated process and requires a detailed consultation that includes a discussion of your goals, a detailed examination, and a lengthy discussion. But the decision will always start and end with the patient. When it comes to sizing, we have all of our patients find 3 photos of their desired breast size. We ask for naked breast photos because clothing can obscure the true size (push up bras). Next, we consult with patients and go over the photos and take detailed breast measurements during a physical exam. Next, we using a sizing algorithm to determine a range of implants that will work based on the exam and the measurements.Lastly, during the operation, we use silicone sizers in the operating room to see how the size actually looks in the breast. We sit the patient up in the operating room, while asleep of course, and compare the sizer result with their desired look photos. If it is too small, we start the process over with a slightly larger implant. We don't stop until we get the perfect match.Of all of my breast augmentation patients, every one of them has been happy with their size due to this detailed and meticulous process. You don't want to invest time and money into a result that is either too big or too small.You should discuss your concerns with a board-certified plastic surgeon and make sure that your surgeon understands your goals.Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery