Advantage-NAAC higher grade is only until you pass out. A higher grade attracts good companies to visit institute for campus placements. A higher grade also indicates that institute is perhaps good in academics, research and placement and attracts prospective students. As a student, you would get to be in the company of merited students in your class. You could get good faculty and enabling academic infrastructure. However, once you leave the college for a new destination, no one will ask whether your college was NAAC A or B grade. Hence, cheer up