I have tried various types and brands of cordage. At one time I kept a hank of strong, hi-tech fishing line in a pocket. Before that heavy braided mason line and before that 550.

I shifted to the fishing line because I was impressed by its strength, lightness and that I could carry a very long length of it. So far so good until one day I had a bit of a pinch. Nothing critical. On a trip to move some furniture in someone else's truck it started to rain. Florida deluges and upholstery don't get along. Soaked stuffing tends to mould.

He had a tarp handy but not a bit of line to tie it with. Figuring this a good time I broke out my line. It worked but it was not an unalloyed success. The line was definitely strong enough. But it was also difficult to cut, even with a nice sharp knife, hard to tie and it was so thin that it sliced into the tarp and skin as I worked to get it all in place with rain softened hands. I certainly had enough, about 50 yards, but would have rather had a tenth as much if it was several times thicker and easier to work with. It worked out and the upholstery stayed dry enough.

But it dawned on me that in a worse, and more critical situation, ease of handling might not be a matter of comfort and convenience. It might be the difference between making it or not.

A quick test:
Get your hands cold and wet. I handle a large piece of ice. Yankees, I suppose, could simply step outside. Then while your hands are semi-frozen reach in and grab you hank of line. Now do some stuff with it. Loop it over a limb while doubled try to use it to assist you in climbing a simulated slope.

Refreeze the hands if necessary and lash a few poles together. Minimum of four lashings. I know you all keep your knife shaving sharp but in a pinch you may dull it a bit. Kevlar can can dull a knife pretty quick. So cut the line with a slightly dulled knife. Using nothing but your hands try to get those bindings really tight.

Again with frozen hands and with time pressure try some knots. Using a vice and pliers check the knots to see how they hold up under pressure.

Try this with Spiderwire or many of the other hi-tech, hi-strength small-diameter lines. You better be wearing gloves with some of these types.

The ability to carry a lot of really strong line isn't necessarily the only criteria. Find your own limits and preferences.

For me 3mm, roughly 1/8", is the absolute low end diameter for such cordage. Your still not going to be able to pull your body weight up even a doubled line without gloves but it is a lot better for being able to pull tight and work with than fishing line. 5mm or about 1/4" is even better but you start getting into major issues with bulk. An on-body kit has to ride without getting in your way or interfering with normal activities.

Kevlar, dyneema and spectra are all very strong but they all have issues. Some won't cut reliably with anything but a dead sharp or special knife or shears. They don't hold normal knots well and even less well when wet. If your going to tie it well and reliably you need to be careful and take your time. Time and care you may not be able to muster in a pinch with frozen hands.

My preference is for nylon or Dacron cord with a tight woven outer sleeve, treated to help keep it dry and hold a knot well. something thick enough to allow me to grip it well with cold, wet hands. Break strength is around 300 pounds, more than adequate for my use. The material cuts easily enough with a less than perfect edge but still resists abrasion and wear.