Dear moda,
Definately the INL increases over the increased input range. INL is the total sum of deviations(DNL) over the full scale range. In the case of sigma delta, as you increase the input range(Voltage), there will be a problem in linearity. This is because for a mutliple order(which could be the case in order to achieve higher bits), there is a problem with the second stage(integrator) getting saturated. Hence some non-linearity will arise. In my experience, if we had a VDD of 2.5 V, we never exceeded the input swing by more than 1 V in order to avoid it.
Also, as per your reference, in ads1271, the INL deviation is about 6ppm which is about 0.3 LSB. I do not think that the INL figures like these will really effect your performance.
I hope that I am clear............