If want a breast augmentation surgery and are having having a saline vs. silicone implants debate, there are really only a couple of differences to consider. Both types are made with an outer silicone shell. The saline implants are filled with saline, while the silicone ones contain a gel-like substance.
Saline implants are a little bit more likely to rupture, while silicone implants may require periodic scans for problems. About one percent of saline implants rupture on average. The breast then slowly deflates as the saline solution is gradually absorbed by the body. The solution is not harmful to the body, and you won't end up suddenly lopsided; it does take time to fully deflate. Surgery will be required to correct the problem.
If a silicone implant is ruptured (which is much less likely), you might not ever know it. There's no indication that the gel substance causes any long-term harm, but it can eventually cause breast pain if it starts to leak out. The FDA recommends that patients get a periodic MRI scan to make sure the silicone implants are still intact.
The only marked advantage for one over the other is arguably for aesthetic reasons: Silicone implants are thought to be more natural looking and feeling. On the other hand, they are more expensive and might leave a bigger scar than if you opted for saline. Furthermore, with improved surgical techniques, such as placement and adjusting the levels of saline, complaints about saline implants have lessened.
If you are considering implants, make sure you find a cosmetic surgery specialist who will go over your various options and help make an informed decision especially right for you.