As anticipated it's just a tad smaller than the primary competitors. Shoulder room and cargo capacity both suffer marginally, although front leg room is impressive. I'm very comfortable with the MKC's dimensions.
Below is a link to a dimensional comparison between the Q5, X3, SRX and XC60. (The Enclave is the "sponsored" vehicle and is obviously quite a bit larger.) The RDX isn't in the chart, but it maintains similar dimensions. You can replace any vehicle in the chart with something else if you want to see how it stacks up. The Rav4 would give you an idea how the NX will compare dimensionally, although the NX's cargo capacity should fall well short of the Rav4's published capacity due to the lower roofline.