The general preference order followed by students is

IIT :-

IIT B >IITD>IIT KGP=IITM=IITK

If you are getting decent department Bombay and Delhi, just chose it .

Choosing IIT Madras completely depends upon you being from South India or not . If you are from South India , I would advice you to go to North IITs or IIT at Kharagpur,Kanpur,BHU. There is not a very big reason for this , reason is just language barriers and your familiarity with environment .

All top 5 IITs are almost same . Just choose according to your interest and proximity to home .

Then comes the second generation IITs

Roorkee > Guwahati > BHU > IIT ISM

Then new IITs.

New IIT ranking continuously change . They will be constant after their 30 years of existence .

Kanpur used to be on top earlier but now Bombay .

Ranking is not constant . They change every year. Thus chose according to your interests and just chill.