What’s the most important thing to look for in a guitar lead?
In a word, reliability. Sound issues aside, premium-quality guitar leads are less likely than cheap ones to fail after sustained use. This is because they tend to have a more substantial outer sleeve, sturdier jack plugs, and are carefully designed to support the solder joints that connect the cable to the jack plugs at either end of the lead.
This helps to stop your signal from cutting out the first time you accidentally trip over the cable or yank it hard. And if you think about it, that’s the most important job a cable has to perform. You can always roll off a little treble on your guitar or amp if your sound is too bright, but you can’t dial away the cracks, pops and hum that a dodgy lead can cause.