Colleges in Vellore

In my honest opinion, out of the choices you've mentioned, IIIT Sri City is the best to go for and there are reasons to support this.
The first and foremost aspect that puts IIIT-S ahead of other colleges is research. The college believes in conducting research programmes that are developmental in nature and provide maximum contribution to the different fields of technology and human nature.
The second factor is the curriculum. We follow a curriculum that is modeled on the curriculum of IIIT-H.
But regarding all other as suggested above, I do not agree. I have crossed over one and highly impressed as I find it as trying to follow and compete with VIT-Vellore and Galgotias in terms of:
(a) Implementation of modern educational concepts and associated internationally renowned faculty from IITs and abroad
(b) Global connectivity by signing MOUs with many renowned technical universities/institutions of USA, UK, Russia and Thailand.
(c) Flexibility for choosing additional courses over RTU, Kota, faculty members, class, class-timing and peers groups of learning.

I would suggest the integrated 5 year degree in VIT because firstly it will save you the trouble of again preparing for GATE exam for doing an B.Tech degree in case you feel interested in your field of study.
Secondly, by doing the integrated degree, you are saving one year time which could utilized more productively.
Thirdly, in case you feel of doing a Masters after finishing your Bachelors, you might get the glamorous idea of doing an MS from abroad which is usually not sponsored unless you join an integrated MS plus Ph.D program. Basically getting a scholarship for an MS degree abroad is really difficult and is pretty expensive (high dollar value against rupees). You can always look for a student loan to pay for the MS degree but why take all this pain when you can get the Masters degree easily by paying relatively cheaper tuition fee in India.