For the reasons you noted, but also because Clinton's impeachment was pretty clearly purely a political act. Trump is all but begging to be impeached for a sustained pattern of behavior that makes Clinton's acts look like jaywalking.

"Impeachment is a win win. "

I don't think there's any way to know that for certain, because we've never been here before. Impeachment may mobilize Democrats, but Democrats, as shown by the midterms and the polls, are already quite mobilized.

I don't buy the argument that not impeaching Trump would demoralize Democrats. There's just no evidence of that, outside of places like DU where we hyper-analyize and overreact to everything. In the real world, everyone on the left and much of the middle understands the threat and will act accordingly.

The impeachment - and Trump's likely acquittal - will mobilize his base. Which base will be mobilized more is a total unknown.

Regardless of impeachment and its outcome, turnout is, and always was, going to be the key in 2020.

He's not Bill Clinton
He's not Nixon (Who resigned)

This is not Watergate.

Congress is not the same.
The electorate is not the same.

Trump will not resign

I highly doubt the senate will remove him, but you never know.

I don't know how this will affect Trump's approval.
However, I tend to think it will have a negative impact on Trump.

More cabinet members will leave and there might be criminal charges for them.

It's got to happen because it's the right thing to do. He has to follow the law. If we don't we're done as a democracy. Also, they're BETTING we don't. They're PRAYING we don't. The weak pushback we're getting is nothing but bluster to try and get us to have the ridiculous conversation about whether we should risk impeachment.

It's congress' JOB to provide oversight.