“I would argue that…” is a weaker statement, because it ends with an implied “…but since I don’t care that much, I’m not ‘seriously’ arguing that.” It’s not at all equivalent to the strong statement “I argue that…”, which has no such qualifier.
Why cure yourself of useful conversational nuance?
Arguably:
- used to say that a statement is very possibly true even if it is not certain (merriam-webster)
- in a way that can be shown to be true (cambridge)
ie. you can be prove it through argument, not “you can make the argument”