Ultimately the pick should be whichever candidate has the best chance to beat the incumbent, because historically the incumbent has advantage to win re-election.
It also means making sure a loss doesn't burn this candidate's chances in 2024.
Also historically speaking, losing party usually wins in midterm congressional elections immediately following presidential elections, so let's hope the trend keeps up. I am more worried about winning state legislatures, where Democrats have lower turnout. DNC really needs to focus on that. 2020 census, which means redistricting -- need to remind people of that.