I think of jarring as referring to shock, where buzzing refers to vibration. A fork that flexes is good at absorbing shock due to its elastic bending - like thin diameter, modern, high-strength steel (OXplat or 853/953, or even CrMo, the venerable Columbus Cyclex or 531 steel). A fork made of material that has inherent energy dissipation properties would be better for preventing vibration from reaching the rider - carbon fiber composite excels at this due to the epoxy binding the fibers together. It's not generally as good at flexing as steel is.