Here's some samples from my playing with them:
There are also other differences such as copic markers are refillable, have replaceable nibs, and label the lids of the markers clearly. I also find copics numbering system to be very helpful when choosing markers. The number of colors available for the Copic Sketch markers is larger than the number of colors available for Prismacolor.
Project Materials: Cardstock (Stampin Up); Stamp (Gorjuss Girl-Sugar Nellie Rubber Stamps); Heart Brads (Provocraft); Sheer Ribbon (Fire Mountain Gems); Color (Prismacolor markers, Copic Marker)