Always opt for the JRF as well as the Lecturership when you are filling up the form. There's no extra study involved after all. If you manage to stay within the top percentile, then you will get the JRF. Too many factors involved including luck to predict it in advance, but if you plan to pursue your PhD full time after this, then you should go for it. Remember though that you cannot keep a full time job along with the JRF.