Most SEOs Say Redirect, Not 404, When Pruning Old Content

Cyrus Shepard posted a poll on Twitter asking SEOs what is better to do when pruning old content, to 301 redirect or 404 the page. That is if the page cannot be updated to have better content, what do you do? Either (a) Noindex/Remove (noindex, 404, 410) or (b) 301 Redirect to a relevant, better page.