What would you conclude from the last 10 test series of --- India v Australia --and-- South Africa v Australia?

SA v Aus last 10 series' results: http://stats.cricinfo.com/ci/engine/stats/index.html?class=1;filter=advanced;opposition=2;orderby=start;spanmax1=08+Dec+2009;spanmin1=26+DEC+1993;spanval1=span;team=3;template=results;type=team;view=series Ind v Aus last 10 series'... show more SA v Aus last 10 series' results:
http://stats.cricinfo.com/ci/engine/stats/index.html?class=1;filter=advanced;opposition=2;orderby=start;spanmax1=08+Dec+2009;spanmin1=26+DEC+1993;spanval1=span;team=3;template=results;type=team;view=series

Ind v Aus last 10 series' results:
http://stats.cricinfo.com/ci/engine/stats/index.html?class=1;filter=advanced;opposition=2;orderby=start;spanmax1=08+Dec+2009;spanmin1=18+sep+1986;spanval1=span;team=6;template=results;type=team;view=series

Seeing the above comparisons, I've got to ask one more question -- why is it believed by many people that SA has been the toughest competitor to Australia over the years?
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