The main difference between the two crowns is the material used as a coping (the underneath part) below the porcelain (which is white).
A porcelain fused to base metal uses various non-precious metals such as nickel or beryllium. These base metals tend to be stronger but are darker and can show through the gums and give a grey-ish appearance if its an esthetic area (front teeth). Some people develop or have allergies to nickel or these metals.
A captek crown contains a high percentage of gold, which isn't as strong as the base metals but because its softer, are regarded to adapt better to the margins of your teeth. Also because gold is yellow, it doesn't have a grey-ish appearance and are generally more cosmetic. Because the gold is softer, there is a possibility for higher fracture of the porcelain on top.
Hope that helps.
Captek is a unique metal gold composite coping for a PFM fixed partial denture. Resulting in esthetic, healthy, strong and long lasting crowns and bridges, you can successfully place in all cases, either natural teeth or implants.
Porcelain fused to metal is the general category, where you have a metal foundation and then the porcelain is fused over the metal. The metal strengthens the crown. But it also makes the crown opaque, and the dental lab has to use opaquers to block out the color of the metal. And it causes there to be a dark line at the gumline, if not right away, then over time.