On the Woodsmith Shop tv show they built a workbench that had MDF as a top. They use solid wood as a frame around the edges, had a vise in the side of the bench and I think they had holes for bench dogs. They may have made the holes bigger and then drop some kind of hard tube (metal or plastic) to insert into the holes.
It great stuff becuase it is so perfectly flat. However, you must seal it. It did not do it and every drop of water will cause huge raised bumps.
I think the best bench I ever built was 3/4 plywood, topped with 3/4 particle board, topped and edged with 1/4" tempered masonite over a 2x4 frame on 12" centers with 4x4 legs. Covered that with 3 coats spar urethane. I'm fairly certain no MDF bench could have handled the abuse I gave that thing.