I agree with exile on the WordPress issue, but I also trust George's qualified experience as admin. Those vulnerabilities can be overcome with proper management. However, if you are building a WordPress AU site, take George and exile's advice and optimize it's design to help avoid these issues. (Fewer WordPress plugins if possible)

As for magento : There are many options available that allow the same shop integration. Conitec currently uses shareit to sell their products. I personally use fastspring. These companies and many others give the same features of using their api to create custom shop pages and checkout systems that will be just as effective in selling commercial products as magneto.