Dear Rajesh,

Both IITs and IIST are better than most of the colleges including most of the NITs and IISTs. For me IIST is more academic oriented institute in India in comparative to any other colleges whereas  IITs as everybody knows best college in India, actually IITs are best not due to it's academic part but due to the other half of the college life which is missing in IIST.

In my opinion if you are research oriented and you need a better job security then go for IIST and if you want a better job and a better experience of college life then go for IIT.

Good Luck !!!!