Fat grafting will be more expensive than implants and many times will require more than one surgery to get the same volume as you would with one implant surgery. To find out which surgery would benefit you the most I recommend having a consultation with an experienced, board certified plastic surgeon.
Fat grafting is an excellent option for patients that want quality and not just enlargement. I been doing fat grafting to the breast for more than 10 years. Fat grafting is more expensive than implant augmentation because it takes longer and you will get liposuction with the fat grafting.