I have both and prefer my Prismacolor pencils for the Gamsol technique. Both have great color selections. I thought I was fine with just the Crayola pencils, but then I tried the Prismacolor - Wow!
I've read that others use the Crayola pencils with the Gamsol, but I find it doesn't work as well for me. I still use my Crayola pencils for some things, but overall I prefer the Prismacolor.
And for the price of the Prismacolor pencils on Viking - buy them! You won't regret it!