Facebook OAuth, WP_Http::request() vs wp_remote_request()

To answer my own question, when you use WP_Http, the transport used is selected, in this order, from this array: $request_order = array( 'curl', 'streams', 'fsockopen' );

If your PHP supports curl, WP_Http_Curl is used. Curl doesn’t support adding the body array parameters when the method is GET

WP_Http_Streams and WP_Http_Fsockopen on the other hand, add the body array parameters.