I will tell you pro and cons of both.

Iiest pros-

1. It is well established college with average placement around 9lpa for cse in 2019 lesser than average iiit and nits for cse.
2. Highly recognized in bengal

Cons-

1. It is more like a regional state college where 90% are bengali. A national college should be diverse like iits .
2. Hostel infrastructure is not appropriate. They pack 4 in single room
3. College is recognized less than iiits in north west and south India among people and professional too. Jadavpur is much more popular than this. Eveyone know the name.

IIIT Lucknow pros

1. Diverse culture
2. Good Coding environment

Cons

1. Almost everything except the pros. The batch from iiitl campus fill passout in 2023.

If your priorities is programming so go for iiit Lucknow.

https://www.careers360.com/university/indian-institute-of-information-technology-lucknow

Hope this helps you.

All the best for your future