Both the colleges VIT Chennai and IET Lucknow are good. I can give you some information about the institutes as I have some friends from both campuses.

VIT:

• VIT Chennai has a very good infrastructure and many clubs, good faculty and you will get great exposure there. But, the placement you get is not up to the mark as compared to the fees you pay.
• The overall expenses including fees are near about 13 lakhs and the average package is around 6 lakhs. I would suggest not to look for top placement as it has a huge batch of students. The ones who get high packages utilize the best of college.

If you think that you can do better and you have no financial problem go for VIT or else IET is not a bad option.

IET:

• IET has a healthy environment as the students coming to the college are very talented.
• Though in IET, very few classes are conducted if you want to give exams like CAT, GRE, GATE, or any other then IET is best for this. At IET you will be free most of the time so you can do whatever you want to do. 
• Also, IET is a government college and it doesn’t cost too much. 
• According to the recent placement highlights the median CTC offered at the institute is 5 LPA.

I hope this helps you in deciding between the two.