I prefer them natural myself. Plus if you're having surgery you really have to make sure you find a dr. that's reputable. There are so many horror stories about surgeries like this that turn out terribly. Then you'd wish you had what you started with. I'd say keep what you have, but ultimately the decision is yours.
ther are other ways of augmentation besides silicone or saline implants... I have a very dear friend that had bi-lateral cancer sergery.. then reconstruction by having lypo-suction done around her waist & the tissue reinjected into her breast.. she went from a full B cup to a slight D cup, they look great & ARE naturalbut enlarged...