What is the difference between Mentor and Allergan implants?

Thank you for the question.  All of the FDA approved breast implant manufacturers provide good products. Each of the manufacturers products differ slightly and each will use different terminology when it comes to describing their breast implants (and each will claim that they have the "newest" and "best" breast implants).  
Personally, I think that careful selection of plastic surgeon and careful communication goals are  the two most important "factors" when it comes to achieving the desired outcome with breast augmentation surgery.  The specific breast implant manufacturer and even type of breast implant are far less important factors, in my opinion.
There are several steps taken to select a specific size/profile breast implant for a specific patient. These steps will vary from one practice to another.  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. 
 
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. For example, I have found that the use of words such as “natural” or "C or D cup” etc means different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup size may also be inaccurate. Again, the use of computer imaging has been very helpful during the communication process, in our practice.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery, after the use of temporary intraoperative sizers.
I hope this helps.  

Hello and thank you for your question.  Allergan and Mentor are two major and competing manufacturers of breast implants in the US.  They each offer a wide variety of sizes and styles to accommodate the needs of most women seeking breast augmentation.  Both the preferences and experiences of your doctor will play some role in which manufacturer or model they will recommend, however, the most important factors in your decision remain selecting the right doctor and clearly communicating your goals to them.  Once you have selected a local, board-certified cosmetic surgeon in your area, you can discuss which implant styles they prefer and which types might work best with your anatomy and why.  
Best of luck!
- Carl N. Williams, Jr., MD

While both companies make excellent implants, they do have different profiles and are manufactured differently so there may be an optimal implant for you. Consult in person with an experienced and expert board certified plastic surgeon to understand your options.