Can you help me understand these 2 VERY different implant size suggestions from 2 board-certified plastic surgeons?

It would be helpful to try on sizers in the two recommended sizes. This would give you a better understanding of how you may look after surgery. It can also help you feel the difference as well, which may be important since you’re a distance runner. Another thing that can help you choose is the surgeon: which surgeon do you feel most comfortable with and which do trust more?

Respect the measurements of base diameter, nipple-to-fold, and tissue thickness for stable long-term results. I agree that 400 cc+ seems much too large for a lean athletic woman.