The yarns are roughly Aran weight, from the same fibers (4 different braids of polwarth/silk), knitted here on US #9 needles.

Photo 1: the swatch overall - bottom half is cabled, top half is traditional 4-ply. (Cable plying means I plied singles A & B together, and singles C & D, then plied AB with CD.)

Most immediately obvious difference is that the colours come out more blended in the cable ply, which I find preferable for this particular project. After removing the pins (and stabbing myself impressively with one - the perils of swatching), the difference in gauge is less obvious, though the traditional 4-ply is slightly more stitches/inch and rows/inch (ie, finer/tighter gauge).

Photo 2: closeup of the two together - traditional on top, cable on bottom.

Now we can see the stitch behaviour a little more. While the traditional 4-ply seemed larger/heavier in the skein, it compressed a good deal with knitting, giving me a less solid fabric and also a slight bias. I expected to see biasing in the stitches from the cable ply as it was less balanced feeling in the skein, but the stitches came out straighter and fuller, and more consistent in size.

Photo 3: just the traditional 4-ply section so you can see the relationship between stitches.

Photo 4: just the cabled section so you can see the relationships between stitches.

The cabled ply yielded fuller, more consistent, less biased stitches, and I like the blending of the colours. Cable-plying it is!

Glad I took the time to sample and swatch this. I did not like the look of the cabled yarn in the skein nearly as much as the 4-ply, but knitted up, it’s definitely preferable. Thanks thorhammer for suggesting this!