There are three typical incisions for a breast augmentation as you mention in your question. In general all three approaches can yield very good results for your augmentation.
Some of the factors to determine the approach are surgeon preference/experience, nipple size, tendency to form scars. Most surgeons have one or two ways that they commonly perform their breast augmentation. You want your surgeon to perform the surgery the way he typically does as they do it for a reason and are very comfortable with that specific approach.
If then nipples areolar complex is very small this approach may not be an option as the implant has to fit though the incision. The areola skin border is a great place to hide the incision as this natural transition of color will make the incision very difficult to see once it has completely healed.
Under the breast or IMF incision is very common as it is a direct approach and in the majority of patients hides very well. In patients with darker skin or a tendency to form thicker scars I tend to avoid this incision as it may not hide as well as other methods.
The axillary approach is great in that it avoids any scars on the breast. With the use of the endoscope the implant placement can be very precise and a traumatic. The natural creases in the axilla hide the incisions and are difficult to find with time. Axillary endoscopic breast augmentations do take additional equipment and training and thus not everyone performs breast augmentations through this approach.
Please discuss your breast augmentation with your board certified plastic surgeon.