Acrylic paint is latex paint, but not all latex paint is acrylic.
The higher the percentage of acrylic in the mix, the higher quality the paint and the tougher the layer it makes. High end exterior paints will be 100% acrylic, at $40-50+ per gallon in the US (vs $20-25 for cheap stuff), I'm not sure what mark up you'll see in Australia or what brands are available.
Check the manufacturers' websites for the specific paint information, they go into very detailed specs and application guides for professional users/bid purposes that they don't bother to include on the cans themselves. For example, Valspar's 100% acrylic Duramax:
Duramax, then select SemiGloss and download the PDF on the right.
For Taubmans, I found they have a lot more information on the professional side of the site:
Pro site, hit Download All Datasheets, page 2 for Endure Exterior Semigloss, and the sheet says it is a 100% acrylic paint.
The paint is the first barrier to moisture entering your tear, 100% acrylic is well worth the extra effort to find and the price you'll pay. You should also use a 100% acrylic primer from the same company to ensure a good bond.