Over/Under Muscle or Dual-Plane? (photo)

Thanks for your question and the photo. Without an exam, it is hard to tell exactly where the nipple position is relative to the fold. IMO there is no reason to put the implant above the muscle. Simply too many downsides to that. I do think that most would use a dual plane technique. You have an asymmetry it appears in the nipple height that will likely be made more apparent when the implant is placed. I would address this with your surgeon. Find a Board Certified Plastic Surgeon in your area that is an ASAPS member and specializes in cosmetic breast surgery. Best of Luck!

When undergoing breast augmentation there are a number of choices which need to be made: saline or silicone? Volume: Larger or smaller? Incision? However, one of the most commonly debated choices is that of implants placement: subglandular/ submammary vs. subpectoral/ submuscular? While many surgeons recommend submuscular placement there are distinct differences to each approach.
 Subglandular Augmentation (“overs”): 
Subglandular augmentation means place of the implant underneath the breast tissue but above the pectoralis muscle. Subglandular placement spares the pectoralis muscle which leads to reduced post operative pain/discomfort and no impact on muscle function post augmentation. Recovery is also fasterSubglandular augmentation can impact mammographic evaluation of the breast. However, as dedicated breast radiography has become more prevalent this has become less of an issue. Fellowship trained radiologists have become familiar with evaluating breasts post augmentation. It is also important to note that implant position does not interfere with visualization of breast tissue via contrast enhanced MRI (the most sensitive and specific study available for breast cancer detection).Studies suggest there is an increased risk of capsular contracture when implants are placed in a subglandular space.Aesthetically, implants placed superficial to the pectoralis major create a rounded, convex appearing breast profile. This effect is camouflaged, at least initially in larger breasted patients. However, as a woman ages fat atrophies and breast tissue descends. The result is a more noticeable implant specifically in the upper pole. Similarly, patients who have thin coverage superiorly are more likely to be able to perceive the implants and at higher risk of visible rippling when compared to subpectoral augmentation.Subglandular implants can also create the illusion of improved cleavage by preferential over-dissection of the central/medial pocket allowing the implants to be forced more to the midline. There is no limiting muscle as there is in a submuscular augmentation. 
Subpectoral Augmentation/Sub-muscular (“unders”): 
Subpectoral augmentation is technically a bit of a misnomer. Traditionally, subpectoral augmentation involves the release of the pecotralis major muscle from its lower attachments. This allows the muscle to “window-shade.” The upper hemisphere of the implant sits underneath the muscle (dual plane). This release contributes much of the discomfort encountered postoperatively by patients.Subpectoral implants have a lower rate of capsular contracture.Aesthetically, in contrast to submammary implants (which are prominent in the upper pole- especially in thinner patients), the pectoralis muscle both conceals the underlying implant and flattens the upper pole. This flattening effect creates a natural sloping as one proceeds from the upper portion of the implant to the lower portion.The most commonly cited drawback to sub-muscular augmentation is the animation deformity associated with contraction of the overlying muscle.With regards to your specific question, in my practice, the vast majority of patients undergo a submuscular augmentation +/- a lift//mastopexy as needed (to avoid a snoopy deformity). Based upon your photos, you would likely benefit from a lift in conjunction with your augmentation. 
As always, discuss your concerns with a board certified plastic surgeon (ABPS).