Dis-advantage, if you practice enough with a single pin there are none.
Sorry, Taz, but I' d have to disagree. It really depends on the setup, and personal preference. There are even those out there that won' t use pins on their compound. And feel that relying on a sight at all is a disadvantage. I won' t use a sight on my traditionals, but will with my compound. However, with the heavier arrow set up and slower arrow speeds, I get a pretty good rainbow effect. As you could see, relying on one pin would make estimating shot placement tougher. I' d rather estimate distance to the game and put the pin where it needs to be.