I believe it may help to consider, for a moment, those two words as rhetorical devices.
Within the rhetorical form referred to as argument there are several important developmental phases including, point of view, audience, persona, etc.
An overarching theme though, is delivery--which concerns the strategy and mechanics of presentation. This consideration answers the question: what is the best approach to win consensus? I'd like to suggest two strategic models: conservative and liberal.
A conservative model takes the posture that the argument is dealing with some given, or set of givens, e.g. self evident truths.
A liberal model does not enjoy such solid support. It must assume a posture granting unknowns, an explicit admission that the unknowable exists. A liberal argument will always impart some sense of an ethical consideration, a qualitative value position. Frequently sentences begin with "In my opinion."
You can always recognize a conservative argument because it is closed, and can not be countered, short of inflicting trauma on the subject.
You can always recognize a liberal argument because it is suggestive and may even encourage alternative interpretations.
It is important to understand that both are useful devices, both are important, both have a place and time.
True of any tool.