Definitely IITs are the premier colleges, the best in the country and some colleges like IISc Bangalore are even considered worldwide. But few NITs like NIT Warangal and Agartala are considered equally good. NITs are tier 2 colleges and IITs are tier 1 but you'll have an excellent career both ways. Most of the companies that visit IITs visit NITs also, only they provide different pay packages there. But some companies even provide the same salary packages for both kind of colleges. Now it only depends on your score that will decide which college you get into. 

IIT is by far the best engineering institute in India and IIT passouts ( in consideration with their grade and overall performance) end up with high end careers and a comfortable life as well. The IITS are also positioned above the NITS in the ranking list. The professors in the IITs are better and more qualified than the NITs. Both IITs and NITs are extremely good in providing education and producing good engineers, but at the same time the top IIT colleges have an edge because of their high standard of studies. Hence if you're long term goal is a good career with a good lifestyle you can use IIT to pursue it. 

Hello Arul,

Both IIT and NIT are great colleges but IIT is considered a bit better considering the quality of education being better at IITs. Also the professors and the faculty at IIT are better than those at NIT and prove to be better in terms of imparting knowledge to the students. 

Both these Institutions are great but IITs prove to produce better engineers due to it having a slightly better edge because of its standard at providing knowledge, jobs and making up good engineers.

I hope this helped. 

Hi Arul,
Hope you are doing well. While comparing IIT and NIT, IIT always bags the first position and NIT stands in second position. IIT is the top institutes in India and NIT is the second top institutes. The recruiters of different tech giant companies mostly prefer IIT and NIT students. Recruiting companies like Google, Facebook and so on take the first choice of IIT when compared to NIT. So placement wise, IIT is at number 1 position and NIT at number 2 position. I hope you got the point after reading this answer.

All the best.