Its probably a SOAP API if its XML?

As far a i saw, they also provide a JSON feed. JSON is way easier too work with. Maybe if you can provide more detailed information, it would be a lot easier to help you get started.

Hi, it is recommending changing from SOAP to REST

Update from SOAP to REST - If you are updating from an older minor revision on a SOAP integration, EAN strongly recommends updating to REST at the same time. Updating to REST now as part of your minor revision updates will save you future development time.

In terms of XML or JSON i'm pretty sure it returns both if you request JSON. Previously though if I remember I had a bit of an issue cross domain using JSNOP, also most of their documentation, coding examples and their sandbox is returning XML, so I found this easier to work with.

Use REST if they support it, XML/SOAP isn't fun to work with

Why is JSON easier to work with? It is because objects are already created and can be easier to integrate with Javascript?

So much for AJAX then..right?