Sorry to confuse you even more but I see disadvantages of composites and amalgams. For most fillings to last, the smaller the better especially on the biting surface. Small amalgams can last a lifetime. Bigger amalgams can stress the supporting tooth structure leading to potential cusp fractures. Composite bonding is its weakest link. Composites can shrink up to 2% during light curing leading to micro gaps and further decay. Furthermore, the bonding agent can be soluble to saliva over time leading to further gaps. Composites do look more pleasing especially on anterior teeth.
I like to use Fuji Equia which is a modern glass ionomer restorative material. It bonds naturally to tooth, releases Fluoride, and has desensitizing properties. It is not as strong as composites although studies has demonstrated similar wear strengths but not as cosmetic.
The best product although fairly new is called Activa by Pulpdent. It is a bioactive restorative material that establishes proper mineral intergration with the tooth. Certain cells such as cementum has shown to grow over this material. I don't see disadvantages other than price.