I have used both braid and webbing jacklines.

Braid are quicker to rig, cheaper, and easier to snap onto with a
double-action caribiner. However they can be hazzardous as they roll
underfoot, and always at the wrong time.

I presently use webbing as its mandatory for some offshore racing. As
they are only rigged when offshore UV degredation is not really an issue.

Incidentally, I rig a single jackstay from the starboard quarter down the
deck inside all shrouds (chainplates are on the outside of topsides) past
the forestay and back to the port quarter. A crew can go down the weather
deck, work anywhere, be foreward of the forestay for a spinacker jibe, and
then return along the new weather deck without any need to unclip and
reclip.

I also have two permanently rigged wire jackstays along each side of the
cockpit. Tethers are attached before crew come up the companionway, which
is a useful safety procedure.

Fair Winds

Graeme