Trading is more risky because you cannot know everything happening in the market. Skill gambling like poker you know everything before taking a decision and this is less risky. They are both risky and they are not recommended. Usually people who play skill gambling have less losses than the other ones.
your logic will be applied for those who played professionally as skills based gamblers really understand how they will take advantage but likewise inside the trade those who also knew how to read the chart can also earn good profits just by reading the movements. both have risk but it will be depend to the person that will take its advantage.