So, I don't know how widely this is known, but there are actually two different carplay interfaces apple pipes to the headunits. One interface, called by apple to be devices with "high quality" touch screen interfaces uses things like intertial scrolling and one to one movement. The other units that have "poor" touch screen response use arrow keys, and sectional scrolling (the list moves the same amount up or down regardless of how much you move your finger or what speed you move your finger across the display.)

What criteria dictates whether or not a device is a "high quality" touch screen radio is not clear. For example, none of the current resistive display NEX Units are considered "High Quality" units. Only the AppRadio 4 and NEX 8000 get this designation. So it would be units with Capacitive displays only? Not necessarily. The Alpine ILX-007 has a capacitive display, but it doesn't get the inertial scrolling interface. 

So demo time! 

Watch the Macworld review of the Pioneer NEX-8000. Watch her move her finger across the menus and see how it scrolls smoothly with her finger movement. 

http://www.macworld.com/article/2843793/72-hours-with-carplay-test-driving-the-pioneer-avic-8000nex.html

Now, watch this Alpine user review of the ILX-007. Notice the appearance of arrow keys on the bottom of the home screen that were not there on the 8000, and to the side of any scrollable list. Watch as when he scrolls in spotify the scrolling is jumpy, and doesn't follow his finger in the slightest. 

Hopefully this is informative. 

Yeah, I noticed that as well. I have the 5000 NEX, the 8000 is obviously better, but I don't know if for my needs it would warrant the price.