Fans say a peaberry tastes sweeter, others say it tastes the same but what exactly is a peaberry?
Coffee grows inside of a cherry fruit and usually there are two coffee "beans" per cherry that grow back-to-back - and where the two cherries touch each other it grows flat but the other side is allowed to grow round. What happens in a peaberry coffee is that sometimes there is only one beans that grows inside of the cherry. Since there is no other bean inside the cherry the peaberry is allowed to grow almost round - giving it its distinct shape.
A peaberry is definitely not a different varietal, and no so much a "defect" as it doesn't affect taste negatively. A peaberry is more like an anomaly.
Peaberry on the left, "regular" on the right.