I have got a rank of 4290 in jee advanced 2016. I want to be in any of the core branches. Is their much difference between old and new IITS. Is it wrong to choose cs in iit palakkad or tirupati?

IIT is a prestigious institution and not everybody gets a chance there but if you have your doubts about whether the new IIT would be able to match the standards of old IITs or not then i suggest you browse for some other universities too. There are universities that have providing their students with the best education, great experience and exposure in many different forms their main purpose and have made a name for themselves in terms of placement criteria. Looking for universities like Nirma University,Ahmedabad.............Lovely Professional University,Phagwara..................Chitkara University,Chandigarh etc. will help you in decision making.