Simplicity? How about never having to worry about where to place what in which Zone and then figuring out f stop and speed that averages those placements. Meter low EV, meter high EV (or look at the scene, and through experience say 8 or 7 or 9 SBRs). Set the aperture and speed accordingly, note the SBR for devt time later, then shoot. One shot! Allows much more time for composition, focusing, and seeing - for me anyway.