I'm trying to think how to explain the difference between the two types of markers, and the best thing I can think of is to focus on two major differences: their opacity and their nib-tips.
For Prismacolors, the colors are very thick and opaque, which is great for coverage (and you will see that every marker piece before this one here from 2006 were done in Prismacolors
), but after the first "layer" of ink, it is fairly opaque, and beyond that, the color you have is solid and that's all you get.
Copic markers, on the other hand, are more transparent, and they come in a lot of colors that are very faint with only a bit of pigment to them so that you can layer them up as if you were doing watercolor or something, which allows for really gorgeous skintones and shadows.
The nib tips are also different: Prismacolor markers have what I'd consider "hard" nib tips that are handy for details, but with Copic Markers you can either purchase them with "Sketch" nib tips, or swap them out yourself. "Sketch" tips are sort of like using a brush pen, and I really like the feel of them.
I hope that answers your questions!
And I will certainly check out your gallery!