The key differences between using self cartilage and foreign material such as a silicone implant are:
Infection risk
Minimal with the use of cartilage; approx 1% with the use of silicone implant
Extrusion (implant coming out) risk
No risk with the use of cartilage, approximately 1-2% with the use of silicone implant depending on technique- cosmetic appearance: cartilage generally gives a more natural softer appearance; silicone implant gives a more defined appearance-cartilage requires a donor site (ear/rib) but silicone implant does not