President Trump has apparently settled the issue, according to the Washington Examiner:
White House counsel Pat Cipollone signaled during a Thursday meeting with key Senate Republicans that Trump has concluded he has more to gain politically from presenting a detailed defense at trial than from no trial at all, said GOP sources familiar with the discussion.
There's more at the link, but that's really the long and the short of it. And who am I to argue with the decision of a guy who has pulled one political rabbit after another out of his hat for the past three years?
UPDATE: Jonathan Turley, law professor and noted impeachment scholar:
TURLEY: I don’t know. Whether this is intentional or not, it seems designed to fail in the Senate. I don’t think you could prove a removable offense of a president on this record even if the Democrats were in control. This thing is too narrow, it is – it doesn’t have a broad foundation, and it’s an undeveloped record. There are a lot of core witnesses that were not called. And the question is why? They said, “We want a vote by December. We want to vote before Santa.” Why? Why – why would you – why would you be pushing this instead of calling these critical witnesses?
TURLEY: They are. And you know, the Senate, the Republicans will be in charge of the rules. I was Adam Schiff’s opposing counsel last time we did this, in the last impeachment. And Adam benefited greatly because the Democrats were the ones who wrote those rules. Now it’s going to be the opposite. Even the Chief Justice in that proceeding does not get the final word. If he makes a ruling on evidence, the majority of the Senate can overturn him. And so the question is, what is this going to look like in the Senate? And I got to tell you, I think this could be the trial that Trump wants. And they will – the first witness they call may be Hunter Biden.