The MPP has more projection than the classic. Most today feel the MPP has a more natural look with better projection. For more information on projection please read below:
For the record one tablespoon is 15 cc's, so 20 cc's isn't that much more. It is very difficult to determine the exact size and shape implant you will require to best match your ideal breast image without an examination by a board certified plastic surgeon. Not just any board certified...
I prefer to choose breast implants that match the breast base diameter. according to your measurements a 350cc would be a better match for you. The 425c is a large implant and your concern about looking "matronly" also suggests a smaller implant than 425cc may be your best choice. For more on...