Which has murdered more
Islam - more. About 270 million in 1400 years.
Communism - At a faster rate. About 100 - 150 million in the last 110 years.
"“We will be studying the deaths of 270 million Kafirs over 1400 years in jihad. That’s 60 million Christians, 80 million Hindus, 10 million Buddhists and 120 million Africans of varying religions.”
This itself cites Mohammed and the Unbelievers, Bill Warner, CSPI Publishing, 2010, pg. 160.