PC's greatest strength in the competitive scene is that all of its players are combined on a single platform. The power of each player's machine will vary, and a special setup may even give some players an advantage, but they are all playing together. The biggest level of separation between PC gamers is servers, and they can easily get around that.
Console gamers are split up by the system they play on, and the competitive community takes a major hit because of it. Pro players are forced to work on whatever system happens to be the standard for the game they play. Then they worry that their league will suddenly switch consoles. Competitive Call of Duty's recent switch from the Xbox One to PS4 is a great example of the problems that can cause.