That brings us to the other, more straight forward, and strongest argument in favor of impeachment. And that is that Trump should be punished for what he did and we should make sure to send the signal to anybody who would consider it again would know there would be severe consequences to doing so.
Given that this would apply whether or not impeachment is concluded before he leaves office, if Congress cannot move quickly enough to remove Trump, it would be better to wait, and make sure it is done properly. Creating the precedent for a rapid fire impeachment could have troubling implications for the future and would raise due process concerns. Again, that might be something you’d be willing to risk to save the country from weeks of his presidency. But if it’s a matter of days, it becomes more questionable.
So if Congress loses the chance for speed — which it likely already has — it would be better if they took their time and did a thorough inquiry of what happened. For instance, Maryland Gov. Larry Hogan has said members of Congress were desperately calling for the National Guard to be deployed, by it took hours for him to get the approval to send them. A more thorough investigation would look into the role Trump played in this.