Hello Kishore, 

SRM is definitely known to be the better university. It has an AAA+ rank. It also provides better campus and hostel facilities. While Guru nanak university is an affiliated college,  SRM is a deemed university.  The Ramapuram Campus is the best in Chennai.  Also SRM has better placement opportunities (with over 240 companies offering jobs to 3000+ students) compared to Guru Nanak college where the placement status is only average and a lot of students have to find work by themselves. 

Hope this helps :)