One way would be to base it on "unders" and "overs".

Bookies give you 1/4 of the win odds for a place - ie 4/1 win = 1/1 place or $2.

Whereas on the TAB, place divs can be way unders. Sometimes, however they represent good value.

Examples
place overs
$9 win; $3.30 place ($3 with bookies)
$21 win; $7 place ($6 with bookies)

Assuming the win dividends represent fair value, if place dividend is above "fair value" then bet for a place - otherwise win bet.