HI Aspirant!

Congratulations for your JEE Rank. According to me you should choose IIIT DELHI over IIIT Lucknow because :

1. IIIT DELHI(2008) is established before IIIT Lucknow (2015) .
2. IIIT DELHI has high package.
3. IIIT DELHI's infrastructure is better than IIIT LUCKNOW.
4. Alumni network is better in IIIT Lucknow.
5. And many more.

At the end the choice is your but I would prefer that you do not waste your next year for preparing again instead you choose one of them and excel your career in that college. You should have in mind that college doesn't matter in some aspect but at the end only individuality matter how you perform.