Considering the sheer scale of infrastructure behind Apple Siri, not to mention usage, it has got to be much more powerful. There is not very much indication that IPsoft Amelia even meets the claims of its maker. Of course, some objective evidence would be independent videos of Siri and Amelia side by side put through their paces, in some situations Siri was good at and some that Amelia was good at. For instance, Siri is a product for consumers, whereas Amelia is more of a CRM agent designed to replace, or reduce, call center staff.
See also my quick and dirty webpages: