I work in and around the Los Angeles area. I have basically settled on the Winegard GhostKiller (7010, I forget the prefix).
It is a medium sized antenna that I have had success with at forty miles from the transmitters. They are all on one mountaintop here.
It has the advantage that it not only attenutates signals coming in from the sides, but also from the back. It is usually not mentioned that directional antennas pick up signals pretty well from straight behind them. Ghosts, for instance.
Anyhoo, I have used this one at maybe eight miles from the transmitters, on hilltops, with hills in the way, with stacks of buildings behind the antenna, and all with great success. You do have to know your amplifying options, though.
Remember, too, that most manufacturers made these antennas into HD antennas by the clever device of stamping the word "digital" on the box. Except for some of the pricy superfazapp fringe buddies, it's just a UHF antenna!