If you're trying to decide between IIIT Delhi and IIIT Allahabad, know that IIIT Delhi is better in many ways.
However, it's true that both IIIT Delhi and IIIT Allahabad aren't as good as IIIT Hyderabad at the moment. That being said, don't be surprised to see IIITD catching up soon, given its impressive progress over the years. In fact, IIITD has nearly doubled its campus size this year, and as a government university, the facilities and infrastructure are shocking - indoor heated swimming pool, stylish buildings and hostels, and awesome wifi speed.
Ultimately, whether to choose ECE or CSE depends entirely on your interests.
It's worth noting that IIIT Hyderabad's ECE program is superior to both IIIT Delhi's CSE program and IIIT Allahabad's CSE program.
It is you who has to decide what you want to study. Ask yourself what interests you the most, what you want to learn. Do you want to learn about signals or you want to know about the computers and the science behind them, their algorithms and working mechanism.
Whatever field you choose, it will stay with you life-long. It becomes more important if you opt for higher studies. Hence, it is highly recommended to self- introspect and choose whatever interests you.
Comparison:
Coming to IIIT Delhi, it is way behind IIIT Hyderabad and IIIT Allahabad. To conclude, choose according to your interests in the respective fields.