I special ordered my MKC, and the 2.0 versus 2.3 engine choice was one that I considered very carefully. I test drove both, although I had the 2.0 for a "date night" weekend, so had more experience with it. Found it to have very adequate merging and passing power with 4 adults onboard.
I always have a bias towards the larger engine in cars (Vette and CTS-V owner), but I just found myself liking the 2.0 better. Plenty of power for my intended use, seems very well matched to the 6 speed, and a little less "turbo whoosh" sound than I heard in the 2.3.
Motor Trend testing indicates 0-60 times of 6.5 seconds for the 2.3 and 7.6 seconds for the 2.0.
I know that the 2.3 is uptuned in the new Mustang and is getting some generally positive reviews. All things considered, can't go wrong with either engine. I am pleased with the choice I made to get the 2.0