The biggest advantage that students are not paying attention is that you will get the experience of giving such a high profile exam two times. No matter how much you have prepared for the first exam, there are often cases when students just freeze in between the exam and have trouble calming themselves and have time management issues. Now you will have the opportunity to rectify your mistakes.
This will obviously benefit all, but now it will depend on how much you learn from your mistakes. Those months between January and April will be priceless to manage both Jee Main and Boards. That will be the deciding factor.
Also, no matter how many books you do, never ever forget to do Previous Years(including subjective). As there are so many papers now, questions will be repeated more often now, or at least similar. Hell, even when there were only 2-3 online papers, still there were 3-4 questions directly related to previous years.