responseContent.size() vs rawResponseData.length

I try to figure out the size of the the soap response.

Like everytime soapUI provides me the the required tools.
But this time it provides me 2 tools and I don't know what's the meaning of the answers.

When I use

messageExchange.responseContent.size()

The answer is: 1466492

When I use

messageExchange.rawResponseData.length

The answer is: 794207

I implemented also a SOAPHandler serverside, where I use the following code:

         SOAPMessage message = messageContext.getMessage();
         CountingOutputStream countingOutputStream = new CountingOutputStream(new NullOutputStream());
         
         try {
   message.writeTo(countingOutputStream);
         } catch (Exception e) {
   throw new RuntimeException(e.toString());
         }
         
         long bytes = countingOutputStream.getByteCount();
         String size = FileUtils.byteCountToDisplaySize(bytes);
         LOG.info("the response size is: " + size);

The result of this is: 793969

So what's the difference between

messageExchange.responseContent.size()

and

messageExchange.rawResponseData.length