This aroused my interest so I did a test on our ratings.
For what its worth:
Over all the performance of our top pick is 26.8% since 2010.
Synthetic tracks have an SR of 28.6% for the same period.

Obviously the smaller sample of 2900 races vs 80,000 may see this normalized with a greater sample.

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Michal - Ratings2Win Pty Ltd
R2W Axis - Axis is Australia's leading horse racing software and database;
with sophisticated form analysis tools and accurate horse performance ratings for TAB meetings.
http://www.ratings2win.com.au/