If weight is really the goal, then steel. Small contours heat up quick in big magnums but still shoot great for the first few rounds. I think of flutes as adding weight. Typically you'd need to go up a contour or two in order to then flute it. Especially if ordered directly from a manufacturer.
If one is already considering a larger contour, then carbon has a horse in the race, especially for larger muzzle diameters for suppressors or big bores
If one is already considering a larger contour, then carbon has a horse in the race, especially for larger muzzle diameters for suppressors or big bores