they are light and strong and expensive compared to the aluminium ones ?
The aluminum ones are heavier and hence I think will be more stable, vis a vis the carbon fibre ones. In windy conditions, the carbon fibre, given it's light weight might not be as stable as the aluminium ones.
If the camera is lens heavy, it is front heavy and a heavier tripod is needed to stablize it.
So, is the carbon fibre tripod worth the expense ?