Both of these implants are good implants and one is not inherently better than the other. There are, however, some differences which may influence the decision to choose one implant type over the other.
Saline implants are made of a shell that is filled with a salt water solution, Specifically, this fluid is IV fluid which is identical to the fluid which flows into your veins when an IV is started in the hospital. Should the implant leak, the fluid will be harmlessly absorbed by your body, and the implant will flatten.
The saline implants look quite nice and are very durable. The disadvantage of the saline implants is that the round ones tend to give the breast a slightly circular appearance, they tend to be somewhat firmer in feel and they tend to ripple.
An implant ripples when the fluid in the implant shifts (generally towards the bottom of the implant when the woman is upright) and because there is less filling of saline in part of the implant, the surface of the implant changes shape and gets waves in it. If there is not enough padding over the implant (meaning not enough breast tissue), especially near the top of the breast, then the rippling may be visible on the surface of the breast as well – commonly referred to as visible rippling. This can be eliminated or minimized in the majority of cases by putting the implant underneath the pectoralis major muscle of the chest wall. (More on this later).
The silicone implants tend to be noticeably softer, the tissues tend to drape over them in a more natural fashion and they tend not to ripple. When a woman feels her breast with a silicone implant, the edge between her natural tissue and the surface of the implant tends to be more obscure and harder to determine. The silicone within the implant flows differently than saline and tends not to ripple even when there is less natural tissue over the implant. Consequently, the tissues tend to drape over the implant in a more natural fashion and the overall appearance tends to be less like an implant. The major disadvantage of these implants is cost as they are more expensive than saline implants. This cost is from the manufacturer not from the hospital, anesthesia or us.