I have one of each of the IQ and PRO 163" coolers in the garage, I could find a scale and give you a weight difference as they are just the exchangers. I was getting ready to use them on a couple of IQR hybrids I'm throwing together over the summer. I don't see the weight of the actual aluminum being much at all, the difference will be in the water volume and that can be calculated fairly accurately with a few measurements.
From my rough measurements and assuming water / glycol at 8 #'s/gallon, going to the wider IQ coolers will be about a 3# gain from water / glycol weight. Roughly another 2#'s in additional aluminum weight from the wider cooler extrusion minus the narrower center skin. (as aluminum is 0.098 #'s per cubic inch, in round numbers)
Essentially add 5#'s, For some that would be well worth the weight penalty.