The only thing I can think of there Tim would be that at the lowest ISO, you may have to go wide-open with the aperture, or expose for longer, which might risk overexposing certain colors depending on the sensor. With wide open aperture, the camera might be more sensitive to particular colors than others - reds for example - and you may blow out that color range a bit.
Personally, I've usually tended towards lower ISOs with fireworks because I'd rather risk some small color clipping to avoid noise, and I like to preserve more of the dark sky ambiance. I've shot Illuminations and MK's fireworks many times, almost always at ISO80 or 100 - and gotten some decent results. I keep my exposures short - 3-5 seconds usually - but long enough to keep the apertures a few stops from wide open.
The rest is all up to framing and timing!