Good question.

I have found that the TABs prices usually follow that of Betfair even after they have jumped.

I saw a 5.50 TAB horse that became the 3.60 Fav 120 secs after they had jumped.
It won.

Betfair had it as a 4.00 Fav

I feel Betfair would be more accurate, so its best to use their prices.

I guess one would have to run a test between the two for this exercise to determine which producers the better results dollar wise.

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Cheers.