What would be lowest risk - new implants or fat transfer after explant due to capsular contracture?

Hello, and thank you for your question. (Keep in mind that an in-person consultation is necessary for the best advice.) There are a few differences between those procedures. Breast augmentation with implants is a one-stage procedure (although subsequent revision, replacement, or removal procedures years later is common). To achieve fullness equivalent to a breast implant, fat transfer to the breasts usually requires multiple sessions/surgeries. But once these fat transfer surgeries are done, subsequent procedures are unlikely. That being said, both procedures have risks. You have to decide which approach is most consistent with your aesthetic goals. If you decide to pursue surgery it’s very important that you find a surgeon whom you are comfortable with and trust and who evaluates you in-person and tailors an individualized treatment plan for you and your aesthetic goals. Best of luck!
Matthew A. DelMauro, M.D.

Thanks for this great question. 
Once you have developed capsular contracture you are more likely to develop it again in the future after revision surgery than someone else having primary breast surgery. The only way to have zero  capsular contracture risk is to avoid breast implants. Under such circumstances, fat grafting is a good option if you are not ready to lose all of the volume that your breast implants were giving you. This operation has its own name - SIEF (Simultaneous Implant Exchange with Fat). 
Interestingly, my impression is that there is better fat graft take during SIEF than during fat grafting of a previously unoperated breast - this might be due to having expanded the breast tissues and skin by the implant. Fat grafting is not without its own potential problems, including early volume loss (around one third), the need to undergo liposuction and to have enough fat "donor" somewhere to do so. However this may be a good option for you and is worth discussing in person at a consultation to assess your suitability. Good luck!