My friend is studying with NMIMS and it's good and easy to get into as well. There are 3 attempts available for NMAT whereas IIFT is a step higher on the difficulty scale. The positive aspect of this is that the crowd at IIFT has intellectuals.
Apart from this, here are some more highlights-
Lastly, you'll have to pay more at both colleges but IIFT would be INR 3-4 lakhs cheaper than NMIMS and IIFT has a stupendous alumni network in the area of international trade. You may now decide based on your future goals.