A few of my friends graduated from VIT Chennai and KIIT and here are some insight from their experience which may be of help.

KIIT will be a better choice just because it's the main campus, the placements are almost at par and you get more freedom to enjoy college life.

But VIT does have an edge over many things, and even if you go to VIT Chennai, the placement opportunities will be the same.

Here are the recent placement statistics for the institutes.

Consider other factors as well, things like which is nearer to your home town, where are your friends going, the fee structure, the branch you are taking, etc