You are absolutely correct with your choice
IIST has a bond of 5 years
and new IITs haent got infrastructure
BITS Pilani is ery reputed and ranked 6th in the country,also u r getting a dual degree
moreoer its just a 4 year course as,the 5th year will be of practice school{where u will be earning a lot :)}
just go to BITS without a second thought
ALL THE BEST
plzzz approve my answer if u liked it
also dont pay fees at IIT as u will not be refunded the 40000 u pay{so,be careful}