"Betfair prices were found to be better predictors of % chance of winning than Tote prices."
"Lower costs and greater flexibility draw in more serious bettors, insiders and Backers wishing to hedge by Laying - all serve to make Exchange prices more accurate."

All above, quotes from various studies. What's your opinion?
Think about the longshot end and Laying opportunities. If tote odds on a horse are 100:1 and Lay price 300, compared to another instance of 100 tote, 150 exchange. Is the difference in exchange prices for the same priced tote horse an indicator of the REAL chances of the horse?
RP

Yes IMO betfair is more accurate and there is significant research showing that the bias for long shots is greatly diminished on the betting exchanges compared to the totes.

That is my impression also. Studies going back many years all came to the conclusion that longshots are overbet on Oz totes.