Another Biden fan here, for many reasons but largely those given by w + a above: he would likely take back the Midwest swing states Trump barely won and hold the states Hillary won. And his rhetoric would fire up the Dem base the way Trump's fires up his base. Yes he is old and has some political baggage, but no older than Trump and holds a change purse of baggage compared to Trump's container load! If he picked one of the moderate young'uns as VP: Amy, Kamala or Corey, he could very well keep voters turned off by his age and style.
All of the above said, someone like Sherrod Brown could end up being a better choice - I know nothing of him now. And Howard Schultz could blow the whole thing up and get Trump re-elected whoever is the Dem nominee.