AJAX .send（）与.send（“”）

When sending an empty AJAX request, are there any technical differences between:

xhr.send();

and:

xhr.send("");

Mainly from a...

• Cross browser support/behaviour (especially this one)
• Actual data sent in HTTP headers (and is it the same in all browsers?)
• The way the JavaScript expression is parsed and interpreted (Memory, CPU usage, parsing time... I know this is very MINIMAL but I would like to know, out of curiosity and for educational reasons)

...point of view.