In an ideal world, it would be 80% Nickel and 20% Chromium, and, round wire would be perfectly round across the entire length with no impurities, no irregularities or kinks, and the wire would come off the spool without any loops and without spontaneously wanting to turn itself into a bird's nest.
In the real world, I vastly prefer wireworks.eu (or twistedmesses.com, for example) over something like, say, Crazy Wire. Because, the latter really does drive more than a few coil builders utterly insane. Premium quality Ni80 wire is smelted by the same Swedish company, Sandvik, that also owns the official brand name called "Kanthal" so, even though it is true the fact there exist multiple brands that use this exact same premium quality Ni80 wire, the size and shape of the spools, and the spooling techniques used to fill them with the wire, all also make a tangible difference in coil building life─despite everyone has to decide for theirself whether this difference is worth going for. For me, it most certainly is.