I prefer dems not to shoot their load prematurely. I want impeachment to be unanimous and to be for very solid reasons unlike with Clinton. When the history books tell of trumps impeachment I want there to be no political motivation and I want the country to be fully united behind removing trump from office. I'm willing to wait for that it instead of getting him on a technicality. I want the next president to feel comfortable filing charges against him with zero thoughts given to whether or not to pardon him.
That makes a lot of sense to me.
Besides, I don't see that replacing him with Pence is any great step forward. The issues are bigger than Trump himself, removing him like that won't solve a great deal. So the only reason I would want to see him impeached is because he's a horrible person and it would be just and appropriate for him to face such humiliation. Less politics, more just the feeling of satisfaction that there is some justice in the world.
An obviously tactical or partisan impeachment wouldn't really achieve the required degree of personal disgrace or sent him into some sort of narcissistic crisis, therefore there seems no point in it.