For a Logitech C910 webcam the MJPEG stream is much faster than any other encoding: http://wiki.oz9aec.net/index.php/Logitech_HD_Pro_Webcam_C910. This is especially noticeable in higher resolutions.
Right now it is transparent for the user which image encoding is chosen for the transport which is not optimal.