Will I see a big difference between 375cc and 415cc Ideal Implants?

It sounds as though your debating yourself about some very specific issues regarding the size you breast implants. There are very excellent sizing systems available to you that will make it clear which implant pleases you the most.

Hello and thank you for your question.  The
best advice you can receive is from an in-person consultation.  The difference between 375 vs 415cc is very difficult to detect.  The size,
profile, and shape of the implant is based on your desired breast
size/shape, your chest wall measurements, and soft tissue quality. 
This decision should be based on a detailed discussion with
equal input from both you and your surgeon.   
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon

Thank you for sharing your excellent question and congratulations on your upcoming surgery.  Though nothing replaces an in-person examination of your breast tissues, based on the measurements you supplied you should see a small amount of difference between 375 and 415cc, all else being equal.  It sounds as if it may be wise for you to "try on" several of the implants so that you can have a better visual representation as to what they would look like

Thanks for your question.  The difference in the two sizes you are contemplating is roughly 10%, which is not a major difference.  However, your surgeon will be best able to tell you which volume is most suitable for your body type.

Thanks for your question.  Since there is no way to say definitively over the internet which size would be optimal for you, take comfort in the fact that the surgeon uses your unique measurements and is able to provide you with a general range.  In many cases the board certified plastic surgeon can best be your guide as they’ve met with you in person and heard your aesthetic goals. You may consider doing 3-D imaging; however with nearly all the breast cases we’ve performed, we’ve found patients enjoy doing a live “try on” session where they actually can “try on” the implant in a non-padded bra in our office.  This does not give an exact measurement of outcome, rather it gives a nice idea of what to expect. For patients who desire a more natural look we like to recommend the shaped implant.  For patients who desire a more full, voluptuous look we recommend a higher profile implant (like Inspira). Remember that all breasts have at least some amount of asymmetry (we like to say they’re like sisters and not twins).  An in-person consult is the best way to discuss your questions.   Be sure to find a surgeon with the following credentials:  *Board Certified by the American Board of Plastic Surgery -- The gold star symbol   *A member of the ASPS (American Society of Plastic Surgeons) -- The circle symbol  *A member of the ASAPS (American Society of Aesthetic Plastic Surgeons) -- the Queen Nefertitti symbol with a Triangle.  Feel free to contact our office, it would be our pleasure to answer your questions in person.  My best, Brian Coan, MD, FACS  

Thank you for the question. Depending on the patient's body type and goals, a 40 cc difference in breast implant volume may or may not create a "clear difference".  For example,  for a more petite patient, even small increments in volume may make a significant difference in final outcome;  for "larger" patients, the same difference in volume may not be clinically noticeable.
Ultimately, careful selection of plastic surgeon and careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, in bra sizers, and computer imaging) as well as careful measurements (dimensional planning) will be critical.
***Given that your surgery is coming up soon, I would suggest that you spend additional time communicating your goals/concerns directly with your plastic surgeon, preferably prior to the date of surgery.
 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” or "increase 2 cup sizes" 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 (and the attached link, dedicated to breast augmentation surgery concerns) helps. Best wishes for an outcome that you will be very pleased with.