A few months ago Velo News published a comparison test of stems and handlebars for stiffness and actual (as opposed to advertised) weight. As I remember, the carbon sets were generally not as stiff as aluminum and the Ritchey WCS sets were stiffer than most and weighed in at the lighter end of the range. The C260 wasn't in the test. 3T was a bit lower down, as was another popular stem, the FSA OS-99. I vote for the Ritchey C260, too.