I think they both just operate differently. Russia lacks money so it's more interested in just destabilizing other countries by increasing divides, promoting populism, playing on controversial topics, manipulating voters and spreading fake news. It's why it loves supporting nationalists and thrives on Brexit and Trump - because these things weaken the West. On the other hand, China focuses more on keeping a tight grip on its own people, controlling the flow of (negative) information and leveraging its interests through trade and economic pressure. It's got plenty of money because of how much control it exerts over its businesses and how crucial the country is to just about every single industry and technology in the world, so it can buy itself into Western companies and use that influence to steer the narrative and protect its authoritarianism. I wouldn't necessarily say one is a greater threat than the other but it's both pretty concerning.