Sewn loops versus figure 8 knots in 6mm nylon; sewn ~16% stronger
CAUTION! This note discusses sewing of rope! Don't sew rope unless you really, really know what you are doing and will test an analogue to breaking! Leave immediately if you are a lawyer or someone who posts on Mountain Project!

Yet another test. This is 6mm nylon accessory cord from Sterling; the sheath is 48% of the mass. The core (52% of the mass) was in just 3 twisted strands, so I doubt this is non-torsional cordage. The cord is soft and easily bent; with just 3 core strands, I was a little concerned about unequal core sampling with the sewing.  (I cut a section and weighed the core and sheath on a jewelers balance.) I used 100 lb test braided Spectra fishing line for "thread" and used at least 60 stitches for each end of each sample. I tried to use different stitching at the ends, but it made no obvious difference in which (of 8 terminations) broke first.

I ended up using four sewn, and four figure 8-terminated sample for the tests. I tried hard to dress the figure 8s well and all the same. Here are pictres of 3 sample of each:
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Here is the test setup. I used a linescale 3 to measure force, and a come-along (More Power Puller) to supply the force:
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The results in pounds breaking strength::

Frankly, I was a bit disappointed the sewing was just 16% better. I think the high stretchiness of the nylon made the hyperstatic Spectra thread more likely to tear through this soft cord. I normally get sewn terminations to be up to 50% stronger than knots.