Its well known that crowd theory produces the best prices. (ie the many always come up with the right price rather then the experts).

But I do agree with you the best test of a ratings method is to compare its overlay/underlay results for laying and betting.

If you can find an accurate rating that consistently outperforms with your laying/betting on the underlay/overlays then you have a license to print money.

Finding those ratings though are very hard to do. And then betting them through the losing runs is even harder.