How to parse XML response using HttpClient in .Net 4.0 to .Net Class?

I have a web service that return xml in response.

Below is a screenshot of he xml response :

<?xml version="1.0" encoding="utf-8"?>
<Root>
<Header>
<Message type="String"></Message>
</Header>
<Output>
<Rows>
<Row>
<Result type="Integer">1021806</Result>
</Row>
</Rows>
</Output>
</Root>

Here is my .net Model that represent the xml response :

    public class ResponseModel
    {
        public class Root
        {
            public Header header { get; set; }
            public Output output { get; set; }
        }
        public class Header
        {
            public string Message { get; set; }
        }
        public class Output
        {
            public List<Row> Rows { get; set; }
        } 
        public class Row
        {
            public int Result { get; set; }
        }
    }

I am using HttpClient Class to send the request the specified web service.

Here is my code :

    using (var client = new System.Net.Http.HttpClient())
    {
         client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/xml"));
         var response = client.GetAsync("myWebServiceUrl").Result;
         if (response.IsSuccessStatusCode)
         {
            var responseContent = response.Content; 
         }
     }

responseContent has three methods :

ReadAsStringAsync()

ReadAsStreamAsync()

ReadAsByteArrayAsync()

What are the differences between the three methods ?

Which one Should I use for xml response and how to parse the xml to the required ResponseModel ?

Any help is appreciated.

Thanks.