600cc, 500cc or in between? (Photo)

Thank you for your question and your photographs.Both 500 and 600 cc implants are certainly
significantly sized.The ideal size is
mostly up to you.That being said, 600
cc implants will certainly make a statement.Probably best to return to your plastic surgeon and try on implants
again.Best of luck.

You appear to have a constricted or tuberous breast deformity and some slight asymmetry.  This may require a periareolar lift to match the nipple location, some work on the parenchyma to avoid a double bubble deformity and a more moderate implant size.  Best to discuss this with your surgeon.  

Thank you for the question and pictures. Unfortunately, online consultants will not be able to provide you with specific enough advice (regarding specific breast implant size/profile) to be truly helpful.  
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. In bra sizers can be useful communication tools also. 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 who makes the bra; therefore, discussing desired cup size may also be inaccurate. The use of computer imaging may be very helpful during the communication process.
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.