Before you argue with someone, ask yourself if that person is ready to hear a different perspective. If not, there really is no point in having a discussion.
Actually, first, ask yourself why you want to have that conversation. Do you want to change their mind? Do you want them to do something differently? Are you interested in possibly learning something new?
Then, think about how the conversation will be received. Some topics need to be introduced very delicately – with carefully chosen words, timing and setting. Some topics will not be received well at all and may be better left unaddressed.
If you feel that it is worthwhile to bring it up, you might start by granting the other person their premise on the issue and then present your perspective. “I know that you feel that we can do this in a slow methodical manner. At the same time, leaving it undone feels irresponsible to me, I prefer to work hard and get it done quickly.”