It's not the width, but the thickness. The width on these two wicks is on the same order. Chemtronics Chem-Wick 0.100" is what it says on the reel. I don't see that size on the chart you linked, at all.
The other brand is a lot thicker (not wider) with larger gauge wires. It feels like it has 3-4x the mass of copper per foot.
I don't know that my needs are particularly demanding. I wouldn't know why one is crap compared to the other. The other stuff works fine and you don't need to move it around as much to a fresh spot while using it. I feel like I use 3-4x as much of the Chem-Wick to do the same thing. I'm sure it's better for certain things that I am not doing, yet. The width is just about right for general use, I think. The Chem Wik is a lot more floppy/flexible. It's like a copper cloth, the wire is so fine.
*Looking at them side-by-side, the Chem Wik is slightly wider, if anything. But side profile it looks half as thick. I can't find my calipers. And now I'm looking, the wires in the other brand are about as thin, afterall. Just not as bendy because maybe it's more material.