In general we recommend completely filling or slightly overfilling saline breast implants because we know from experience that if the implants are underfilled significantly, there is a higher chance of rupture (the edges of the implant fold and rub against each other and over time the wall of the implant weakens. I don't think overfilling the implant will make it look or feel too much different, and if your priority is the best look and feel, the silicone implants are the best choice.
As a basic principle, I always encourage a patient to choose an implant which has a "footprint", which will fill their chest. The choice of "profile" depends on how much superior pole (area between the collar bone and nipple) fullness they'd like to achieve as well as what their native breast tissue provides. For example, a tight chested young individual may target a more projection (high profile) than a post pregnancy woman who wants to modestly fill up her skin brassiere (moderate plus). Interestingly, the practice of overfilling saline implants can mitigate against palpable lateral edge wrinkling, however the overfill imparts a rounder, more narrow appearance to the breast, which not everyone appreciates. I tend to look for not only soft tissue asymmetries (nipple position, volume discrepancies) but also bony chest wall differences in the consult. It's always easier to explain to a patient preoperatively, why we recommend different volume fills, rather than post facto. Good luck.
