Physically, if you can see the pictures, the Challenger is a translucent white type of string. The regular Synthetic Gut (in this case white--black is similar but has the coloring) is that "pure white" (more a plastic-type outer layer--though not the most plastic, surely by far, for syn guts on the market) type. The Challenger is very pliable.
When playing, the Challenger does tend to move more. As far a spin, they are both nylon, so you're getting the spin you put into it with your stroke (as with any, but the spin isn't accentuated).
Touch I think will depend on your response to how the string feels to you. I wouldn't say the Challenger is "mushy," just soft, as the ball is "pocketing."
Also, the Challenger isn't particularly powerful, but it isn't dull either with the pop that you do get. I use all these words relative to the strings mentioned, not to the overall world of strings.
The Challenger is a very "hum drum" string in my opinion.