In reflex based games, given two otherwise equal setups with players having equal reflexes, the one who gets the stimulus first due to higher refresh rate will win. The standard 60 Hz means new data is sent every 17ms. With 144 Hz you cut it down to 7ms. With equal reflexes, the player who receives the stimulus 10ms earlier will execute the necessary actions 10ms earlier.

In practice no two players are that equal, but it's still beneficial to accumulate every advantage you can.