I have both and use the Work Sharp for major re-profiling and on odd sharpening things, like an ax, or other garden instrument. When sharpening a knife with a lot of grinding needing to get a new shape, or repair a broken tip, etc, I use the Work Sharp, and then finish up on the paper wheels. For most of my knife sharpening, I use the paper wheels for a quicker and sharper job. Get both, if you can afford to and you won't regret it.
Blessings,
Omar