I've worked with carbon fiber for 30 years... The problem in making comparisons is that metals have isotropic properties, meaning they have the same properties in all directions. Composites are anisotropic and only have mechanical properties in the directions fibers are placed, like the grain in wood. There are also many different carbon fibers, with different properties.

For example, and these numbers are rough but close, steel is typically somewhere around 100,000 psi in tensile strength and there is a carbon fiber that is almost 1,000,000 psi in tensile strength, ten times as strong. If this fiber were used to make tubing and all the fibers were oriented lengthwise, the tube would normally be around 60% fiber and 40% resin, so the tensile strength would be about 600,000 psi, six times as strong as the steel. The problem now is that this tubing could easily be crushed and wouldn't handle any torque, so fibers also have to go in those directions, further reducing the multiplier for tensile strength. Next problem is this particular fiber, 1,000,000 psi tensile strength, is hundreds of dollars per pound and used mostly in aerospace applications and not in bicycles. The fiber usually used in bicycles is around 600,000 psi in tensile strength to begin with, but then fibers need to go in several directions, so you can see that to get sensation on TV, it might be a truth to say there is carbon fiber that is 10 times as strong as steel, but it won't be realized by the time it is in a useable product.

In terms of stiffness, there is carbon fiber from 33 million psi modulus to 135 million psi modulus (this one is $1500 per pound, raw on the spool) and steel is about 30 million psi. All the same rules apply as far as fiber % vs. resin % and mixing different fiber orientations to make a complete product, so again the multiple depends on the fiber used and the use the tubing has been designed for.

The density of carbon fiber composites are actually 1/5 that of steel, but by the time you have fibers in all the needed directions, the wall is usually thicker than a steel tube designed to do the same job, so you don't usually get a product that is only 1/5 the weight of steel.

The fatigue life of carbon fiber composites is much longer than any metal and is actually ignored in many designs, and there is no corrosion, but carbon fiber composites can not take near the impact that metals can, so again - which one lasts longer? Depends on use and care.

I don't mean to write a textbook here, just hopefully clear some confusion. My point is that you can't really make a simple comparison that defines a multiplier for carbon fiber in general being "stronger" than steel. There ar elots of good frames out there in all materials. What we ride is really just a matter of personal choice unless we are so elite we should be thinking about the Tour de France, etc...