Saline and Silicone breast implants have a similar outer shell which is made of silicone.
The difference lies in the material that is used to fill the implant - silcone vs saline.
In my opinion, technology with Silicone implants have improved to such an extent that saline implants have gone the way of the dinosaurs.
Silicone implants have lower rupture risk. The gel is now cohesive so that even if the outer shell breaks the silicone does not flow out of the shell.
The newer Silicone implants have a soft gel so that it feels very natural and mimics the way breast tissues change with posture - tear drop on standing, rounder and flatter when lying down. Texturing of the outer shell has become a topic of debate recently. I find my practice veering towards smooth or nano-textured implants in the light of recent medical evidence.
So in summary I would say Silicone better.
