Vent ribs are almost universal these days, and they are supposed to help dissipate heat and dampen mirage. In reality, a solid rib makes more sense for most field shooting, where we rarely shoot enough to heat our barrels. Solid ribs are hollow, if made right, and they don’t weigh more than a vent rib. Some old Superposeds had solid ribs. The only ones I can think of off the top of my head these days on production guns come on some Caesar Guerini guns. They look good and have the advantage of being, well, solid, so they don’t snag grass and seeds and things. They’re easier to keep clean, too, because you no longer have to scrub the underside of the rib and the posts with an old toothbrush.