Curiosity got the better of me and I had to run some figures for NSW.
Just doing figures on races the NSW Tab had a pool on (41700 races overall)

Betting on the SP Favorite SP returned 89.88%, Tab returned 89.74%
Betting on the longest (SP) priced horse SP returned 36.97%, Tab returned 44.52%
Always picking the winner SP returned 683.13%, Tab returned 790.76%

As I suspected the SP prices are particularly miserly in WA. I've noticed when trying to bet to a price over there that I usually go for best div and rarely take the set price being offered wheras it's about half and half in NSW.
Not much between SP and Tab on the favorites but Tab is more generous the longer the price becomes.

KV