There are basically three types of crowns --
GoldGold crowns are strong.
They are about the same hardness as teeth so they don't wear the opposing tooth any more than normal.
Gold crowns require less lab costs, so they are less expensive.
Many people choose gold for crowns in the back teeth.
Porcelain fused to metal (PFM)
The tooth colored porcelain is fused to a metal casting underneath.
PFM are the strongest of tooth colored restorations.
They work well for bridges.
No light can penetrate the metal coping under the porcelain. If the gums recede to expose an edge of the tooth, the exposed edge will typically be darker than normal because it's dark under the crown.
Full Porcelain
Porcelain crowns are the most esthetic (real looking) crown possible.
Light can penetrate the porcelain. If the gums recede to expose an edge of the crown, the exposed edge will typically be the same color as normal because the reflected light from the inside of the tooth is the same as normal.
Where possible, Dr Fred recommends full porcelain for anterior teeth. They are fine for most posterior (back) teeth, but are not quite as strong as PFMs. PFMs are usually best for the back teeth.
The lab costs of full porcelain are higher than other crowns, hence they cost more.
New porcelains are strong, but not quite as strong as PFMs
Bridges of full porcelain are slightly more prone to breakage.than other bridges. Hence full porcelain bridges are limited to 3 unit bridges. If full porcelain bridges break, they can be replaced, but usually requires a bit more work with the drill to remove the remaining part of the old bridge.