Steam has more than twice the active users than there are Playstation 4 consoles sold though.
Do we have any more up to date stats? Because back in August 2017 valve reported the MAU's for steam was 67m not 166m.
March 31st 2018 Sony announced PSN MAU's was 80m. So unless Steam grew by 20% over those 7 months for some unknown reason, PSN has more active users.
I do believe Data downloaded through Steam is higher than PSN though and just not shown in this chart.