Some info, for science...
As for the appearance, there is not a major difference that Silicone has over Saline, except rippling. Rippling of implants occurs when the folds of the implant shell become visible through the skin. Silicone implants have a very little tendency of rippling, especially in cases when patients are slender.
The major factors that can determine the possibility of rippling showing through skin include: if the tissue or muscle or fat covering the implant is a good amount, rippling will not show through the skin. The another factor is the filling of the implant that matters. Since Saline water is low in consistency, therefore implant shell can easily fold against saline, but for Silicone, the consistency is way more.