I'm going to go against the grain here and say that the better choice of sight is the one the shooter is most comfortable with. If the gun is to be "use specific" as a protection rifle, the functionality of the piece is more important than aesthetics, accuracy, or power. While I believe that the ghost ring rear and a rectangular front post is the best solution, it is only the best solution for me. An express sight can be very fast for the man used to it, but IMHO you must pay close attention to the style. The V in the leaf should be shallow, providing for a fast index to center the bead. The deeper the V, the slower the sight is to use. If you choose an express sight, consider a blank leaf that you can regulate for elevation yourself. A single leaf is better, as some have concerns about a long range leaf standing up from the recoil of the first shot, and it is a common practice to remove the folding leafs from the sight.
From what you say, you have experience with the ghost ring, so if you can snap shoot effectively with a ghost ring equipped rifle, that is probably the best solution rather than having to learn an unfamiliar system.
