I think it is unlikely that fivethirtyeight.com would be more reliable. The human minds are still more subtle than statistical methods alone. However even if 538 did prove more accurate its results would soon be incorporated into the market by betters. The reverse is not so likely to occur.

> Now, if there were a US-legal prediction market, that would be something.

You would have to think that involving US citizens would improve the market's accuracy. It's ironic that US-citizens can't bet.