the H6D has a best in class touch UI...
Thanks for catching my error. That was meant to be under the XF not the IQ.
The XF touch screen is quite handy especially for accessing advanced settings. For example to set the max-slowest shutter speed for Aperture Priority mode you tap on the shutter speed.
Finally, the XF is an excellent tripod camera but I find the H6D superior for handheld shooting thanks to its more compact, lighter body and superior mirror damping.
I'd say 2/3rds of our clients are using the XF handheld all or most of the time. Personally I use it handheld 90+ percent of the time. A lot of our tripod shooters are actually using a technical camera, thanks to the excellent workflow ease and hardware integration P1 maintains with technical cameras.
The H6D-100C is 2130g with an HC 80mm lens and batteries and card.
The XF IQ1 100 is 2638g with an 80mm Schneider LS Blue Ring and batteries and card.
So the H6D is ~80% the weight of the XF IQ1.
Most of the difference is because of the larger/brighter viewfinder of the XF and the use of more metal in the body.
If you're looking to shed a few ounces from the IQ and don't need fast flash sync with strobe then you could change the standard Viewfinder to a Waist Level Viewfinder and 80mm LS BR for an 80mm D which drops ~350g respectively and ~200g to a total of 2088g (you could also switch the hassy viewfinder to make it ~200g lighter for a total of 1930g).
Size wise the two systems are extremely similar. The XF is about ~0.5 inches wider and they are within a few mm of the same height and depth.
Of course, everyone is welcome to their own opinion as to which fits their hand better, which user interface they find more intuitive, and how much priority to assign the difference in weight/size.