Ed Balls would be a disaster, so would David Miliband. How do I know? Well I predicted Brown would lose us votes even before he became PM. Image matters whether we like it not. Balls is fat and comes across as pompous.
I would pick the best looking person with good communication skills - which, of the limited choices available, leaves Jon Cruddas and Ed Miliband. I am on the left, so Jon would be my choice.
Sadly Labour members are likely to choose neither because the party has become so hollowed out only neanderthal tribalists, charlatans and nerds are left in the party. And none of these have got a clue about public opinion.