There's no such thing as 'best' power cord for anything. If it exists, then everyone will be using the same power cord.
It all depends what you're trying to achieve, power cord is just a means of 'tone' control, even though some manufacturers try to convince you that their PC are 'neutral', don't buy into any of the hype. The only way of ascertain 'neutralness' is via measurement. Unfortunately human hearings are not created equal, hence 'good' measurement does not necessarily translate into 'good' sound.
Hence when you seek advice on cables, it is best to describe what you're currently using in your system, and tell people what you like/dislike about your current system.
