Why does WCF return myObject[] instead of List<T> like I was expecting?

I am returning a List from my WCF method. In my client code, it's return type shows as MyObject[]. I have to either use MyObject[], or IList, or IEnumerable...

WCFClient myClient = new WCFClient();

    MyObject[] list = myClient.GetMyStuff();
or
    IList<MyObject> list = myClient.GetMyStuff();
or
    IEnumerable<MyObject> list = myClient.GetMyStuff();

All I am doing is taking this collection and binding it to a grid. What is the best object to assign my returned collection?