Originally Posted by roadwarrior
Most carbon frames are really designed to be racing frames. Aluminum is all over the place from hybrids to mountain bikes to touring and heavier duty riding frames...they are a bit heavier, but are more durable and comfortable.
Think of it this way...carbon is like a sport suspension in a car...stiff but very responsive. But not real cushy. So it depends on what you are after. Responsiveness like a racer, or a softer ride for fun cycling.
I believe you are incorrect in your reasoning and understanding - alum as a structure is no more durable than a carbonfibre epoxy frame. Esp when lightweight is wanted - alum tubing becomes extremely thin.
Cannondale's CAAD7 is a good example - it is an ultra light frameset made completely of alum, to sacrifice for the light weight - the warrenty is only at 2 years with aggressive riding (whereas Cannondale usually gives a lifetime warrenty).
Carbon frames are no less cushy than alum in general - alum utilizes oversized tubing - which usually results in frames that are plenty stiff, if you want comfort, go for steel.
But the comparison between alum and carbon is false - the reason why carbon isn't used more often in general applications is because it costs more to develop and research - alum is just more cost-worthy as a beater bike because it is so darn cheap to use.