If I want to replace 700cc HP silicone implants for bigger 1000cc implant, do you recommend silicone or saline?

Thank you for the question and pictures. In my practice, I utilize overfilled saline filled implants for patients who want the "extra large" look. Patients undergoing breast augmentation surgery with these sizes of breast implants should be aware of the  possible physical and psychosocial downsides associated with larger breasts.   You may find the attached link, dedicated to "larger" breast augmentation surgery outcomes helpful to you as you learn more. Best wishes.

You are already drastically oversized for your body. I am not aware of any company that manufactures saline or silicone implants at that size for very good reason. Your implants are migrating due to too much weight with too little skin support. think what will happen with larger ones!!