There's no need for them to be either stiffer or less stiff; it depends which carbon bars and which aluminium bars you choose to compare. At the limit, you can make a carbon bar slightly less stiff while remaining reliable, because aluminium ones will fatigue very fast if they are designed to operate at high stress, but typically carbon bars will be stiffer than aluminium bars of the same outline and weight.
My point was that the carbon bars may not be particularly stiffer than any other bar. As with frames. If I've understood all the talk about using carbon over the years making a frame using carbon means that you can make it flex where you want it to. So you still have a bike which is stiff but at the same time it flexes enough to make it comfortable. Also there's the weight, or lack of it.
As you mention there's the weight:strength ratio.
Going back to the point of the stem. are you really going to notice a massive difference in stiffness by using a carbon one? The only time I've noticed a real difference in the stiffness of a stem was when I went from a cheap 2 bolt 120mm to an expensive 120mm 4 bolt.
Changing that stem to me seems to a a pointless action. As with replacing a standard SLR saddle with a full carbon unpadded saddle. More shiny shit for a marginal weight loss
My point was that the carbon bars may not be particularly stiffer than any other bar. As with frames. If I've understood all the talk about using carbon over the years making a frame using carbon means that you can make it flex where you want it to. So you still have a bike which is stiff but at the same time it flexes enough to make it comfortable. Also there's the weight, or lack of it.
As you mention there's the weight:strength ratio.
Going back to the point of the stem. are you really going to notice a massive difference in stiffness by using a carbon one? The only time I've noticed a real difference in the stiffness of a stem was when I went from a cheap 2 bolt 120mm to an expensive 120mm 4 bolt.
Changing that stem to me seems to a a pointless action. As with replacing a standard SLR saddle with a full carbon unpadded saddle. More shiny shit for a marginal weight loss