If you are looking for a sunroof, you will have to remove the Maruti Fronx and Toyota Urban Cruiser Taisor from your consideration set, as neither of them gets one. Between the Tata Nexon and the Mahindra XUV 3XO, the Nexon is a better bet because of mileage and overall cabin space.
So go ahead with the Tata Nexon. In your budget, you can even look at Nexon Petrol DCT, which is a more responsive transmission than AMT.