I tried various materials over the years and like the UNI 6/0 best for most of my fishing, trout leaders 7'-6" to 12'-0" long, 6x to 4x tippets. Comes in many colors, including hot pink for strike indicators. I get about 2 1/2 leaders per spool.
For those who are interested here is a short list of other materials I have tried...
clear mono sewing thread = too difficult to work with, breaks and tangles easily.
STREN 1 lbs/2 lbs spin casting line = doesn't hold paste float as well as the uni 6/0
tippet material = too expensive, harder to work with.
silk sewing thread = extremely limp, not as strong as uni 6/0, can be damaged by mildew and sunlight.
Danville 6/0 tying thread = too limp for my taste, although some friends prefer it.