Not all statements are arguments but arguments are infinitely more useful in this game than any other function of communication. An argument presents a relationship between a claim and a conclusion through reasoning; and in doing so provides players with lots very valuable information. In contrast a statement of opinion is a relatively useless function that allows for very little analyzation.

From an argument a player can:
Understand its author's reasoning and place measured value on the position it supports
Examine the reasoning in the argument to analyze the motivations behind posting the argument
Compare the presented reasoning with the projected level of certainty in order to identify the potential of the author having knowledge that is not common knowledge
Examine the perspective that the author is speaking from
Identify and eliminate bias in their own reasoning on the subject at hand
Identify that its author has taken a position on a subject

From a statement a player can:
Identify that its author has taken a position on a subject

When you make your claims in the format of an argument people will trust you more because they can understand how you reached this conclusion. You will be more widely town read in most situations, more effective in persuading people to follow your point of view and push the game forward