I am sure all of you hear about copic markers. They are all the rage and people are creating some wonderful works with them. Prismacolor also makes a comparable marker (alcohol ink marker). I mentioned a couple days ago that I purchased some at the university art store to try out. I picked out four colors of dark red that I thought I would be able to blend together.

Here's some samples from my playing with them:

Cost: Prismacolor: $2.49 each, Copic: $6.49 Prismacolors have a stronger smell. I didn't find it off putting, but I wouldn't hold it up to my nose. If I was coloring more than a small image, it might be irritating.
One of the biggest differences is the pen nibs. Prismacolors have one large nib and one fine point nib. Initially it was off-putting, but I found it didn't take that long to get used to using the larger size nib (you have to turn it over so the triangular side is pointing down--this is the opposite way to what I consider instinctual); I will say I LOVE the smaller fine point nib for adding the shading. I wish I could get a mix of the two: the super nib from the copics and the fine point nib from prismacolor in one pen!
Another big difference is the way the marker colors. With copic markers, you can color and recolor an area without darkening the color. Take the example below. The heart on the right was colored with a copic marker. The LEFT side of the heart was colored twice and the right side only once. You can now compare the side of the heart colored twice to the side of the heart colored once and beneath it, the original color. Notice on the Prismacolor there is a much larger difference between the two halves of the heart.

Thus when coloring the prismacolored items, you can not simply use the lightest color to "blend" your maker colors together. You could however just use the same marker and achieve shading with only one marker.
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.
Overall, I would say that I prefer the Copic markers at this time, but I am intrigued by the Prismacolor markers and consider them a good alternative. I would like to spend more time developing my techniques with them and will give more feedback to you later. I also want to experiment with blending the two marker types together. Keep your eye on the blog for more data on these markers.
Here's the final card I made with one of the colored images:
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)