The data continue to suggest Biden is a stronger candidate against Trump than Sanders. Below are some data from G. Elliott Morris, who does political data for the Economist, and from Alan Abramowitz.
They clearly show Biden is better overall and in swing states against Trump than Sanders. If the election is not close and favors the Democrats, perhaps either of these candidates could win. But if it's close, Biden's superior appeal could mean the difference between victory for the Democrats and defeat.
Therefore, we come back to the point I made yesterday: the Sanders electability case rests entirely on the assumption that his candidacy will send turnout through the roof, while Biden would leave many voters sitting on their hands. That Sanders' turnout bonus would supposedly make up for any differences in candidate appeal we see in the data right now.
Tomorrow I will examine the plausibility of this assertion in light of data from 2016, 2018 and recent polls.