Both colleges are in same city and offer same course but you will learn different things in both place.

IIIT is coding oriented most of the ece guys do coding here and give less focus on core ece on the other hand in mnnit ece student study ece bit more and core ece study is better there. But iiit has far better infrastructure and labs when compared with mnnit.

So I 'll conclude by saying that iiit has more flavour of coding(IT) in its ece while mnnit offers better core ece. Placements wise both or equal but environment and culture of coding is far better at iiit.