Where do you want to go? Your thoughts and aspirational travel ideas create the best value for your points.
This will probably determine the starting point for the most cost effective place to convert your points. Westpac has their own low value travel redemptions. Points can best be used by transferring them to one of the supported airlines ie Air New Zealand, Malaysian Airlines, Singapore Airlines or Virgin Blue Velocity.
For instance, converting 300k Altitude points will go to Singapore Airlines as 150,000 Krisflyer miles. That's enough for return Brisbane - Amsterdam in Business Class. The same points could get you three return economy flights Brisbane to Singapore. Or even 5 return flights BNE - Cook Islands.
So you have enough points to go anywhere in the world. Let us have a clue on your favourite place to visit.
PS: Of course, the points can be converted to Virgin Blue and you could do lots of intra-Australia travel but not as much fun.