The way I am experiencing this while doing a quite a few demonstrations on the IQ180 (prototype) and the Aptus II 12 this week is, that there are simply those who want the resolution , but don't need all the bells and whistles.
I have met with a variety of types of photographers and I can sum it up simply like this.
The studio professionals who soot tethered the majority of the time who were really excited about the IQ when walking through the door loved it, but then when we put the Aptus II 12 on the tripod and took the same shot, they saw virtually the same file @ $12k, less and most said "I really don't need the display because I shoot tethered, I don't really need USB3 and some of the other great features, but were torn with Sensor+". Sensor+ on this large of a sensor is very useful because the files are humungous! They also experienced the tethered live preview was a little better on the Leaf in Capture One, and also more of an improvement in Leaf Capture.
The location shooters (Architectural, Landscape, Social) felt the opposite in most instances the were all over the IQ even with the the price premium because they loved the all the features especially the display. Being able to check focus at 100%, the tilt sensors and the concept of live view on the back itself.
Heck they both shoot to Capture One , so the shooting part was seamless,a s well as the processing and editing between the two systems. Of course with Leaf you have the added benefit of using their excellent legacy Leaf Capture Software.
They are both supported by PhaseOne as a company and us as a reseller which handles both lines is a big plus since they could compare them side by side. So either way they were feeling very comfortable and impressed with the both systems overall. There is also huge support network out and installed base of both Leaf and Phase worldwide.
From what I saw the file quality (mind you the IQ is a prototype) looked virtually identical , but the color was different. That is because Leaf and Phase One used different color tables. It was not that one of them had better color. It is like what has been discussed here before Leaf and Phase have their own characteristic looks.
I feel that this is great time for the photo industry because there are more options available at a variety of pricing levels.
Just like Guy mentioned its similar to the auto industry, you can get a Toyota or a Lexus , they may both share the same engine and get you from point a to point b , but it is the amenities that are different. So options are good.
Lance