With a single front bead, you could be looking directly over the bead and not aligning it flush with the rear receiver. All shotguns and various loads will impact/pattern differently so it's good you tried it out. While you could more than get away with the front bead with some more practice and holds, I prefer ghost ring sights. They're very accurate, reliable, and often cheap.
Nothing wrong with a holographic type sight as there are many on every price range. However, when my life is on the line I do not like to rely on the possibility of a battery or electrical problem and it not working. My shotgun for work is a 14" 870 with a single front bead and it works well. My personal shotgun/off duty has a ghost ring and I greatly prefer it.