No question, a peep will allow you to be more accurate - but it's advantage is very, very small for a prepared hunter. A guy shooting paper in a tournament will take every advantage he can get. I'll do the same when hunting, and that means not using a peep. A 1/2" "flyer" is still a dead deer. On the plus side, nothing obsures my view of the animal, nothing to cut down on the light entering my eye, and nothing stuck to the string that could have a problem.

Peeps are prone to turning at inopportune times, clogging with dirt, water or ice. They can move, break or any number of things that can't happen if they aren't there. Without a peep, I can anchor and shooter faster - much faster. Small windows of opportunity don't get by me. I'll bet the average peep shooter takes 3-4 times as much time to get a shot off, as I do.

It takes practice, but you can learn to shoot without one and be good enough that no one will notice by looking at your groups. Once you learn to shoot good without it, every advantage goes to the hunter not using one.