Is there much difference between 425cc and 500cc mentor high profile implants?

Thank you for your question.  The difference between these implants in not big, but you should speak to your surgeon about this issue

Hi.  You have spotted the problem with using off-the-shelf implants that can't be adjusted at the time of surgery, which is that you are limited to the sizes that the manufacturer provides.So, if correction of asymmetry is your #1 concern, then stay with the sizes in the 400 cc range where there are more choices, which will allow better matching - or choose a saline implant, which could be adjusted.If size is the most important thing for you, then you may have to give up on your goal of asymmetry correction if you choose the silicone implants, as there are fewer in-between sizes after 500 cc.

Thank you for the question.  Yes, a difference of 75 cc may make a significant difference in the outcome of breast song rotation surgery, depending on the patient's body type and personal goals.  You may find that your plastic surgeon will have access to different manufacturer's breast implants that may  provide  breast implants closer to the sizes you are considering.  Generally speaking, it really is NOT in patient's best interests to heed the advice of online consultants when it comes to be specific breast implant size/profile that will best achieve their goals.   Again, 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. Sometimes, it is necessary to seek several consultations before you feel comfort will about your choice.
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. 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, best not to discuss your goals and/or judge the outcome of the procedure performed based on achieving a specific cup size.  The use of computer imaging may be very helpful during this communication phase.
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. I generally select appropriate breast implant size/profile after the use of temporary intraoperative sizers and viewing the patient's chest in the upright and supine positions.
I hope this (and the attached link, dedicated to breast augmentation surgery concerns) helps.