I'd go with a peep sight. Peep sights are easier to get the proper sight alignment with becausea persons brain instinctively tries tocenter the front sight post in the peep aperature. Peep sights are both fast and accurate. The militaryhas used peep sights onmost of it's rifles for the last75+ years for a good reason. Just make sure that theaperaturesizeyou choose is suitable for the conditions you intend to use itfor. The M16A2+/M4 series rifles havetwo different aperatures, a small one for daylight and long range, andthe large "0-2" sight for short range and nighttime use.A smaller peep willbe more accurateto longer ranges, but will not allow much light through and will be next to worthless at dawn/dusk. The opposite is true for a largeaperature;somewhat less accurateat all ranges, but usable in low lightconditions.

Mike