Going to necro-bump this old thread since I just test drove a Q5 diesel today. Just wondered how others felt on the Q5. I was already not thinking I'd be going for a Q5, but I was finished early at work so I thought why not swing by the dealer.
My opinion was just wow, the Q5 is dated. I was pretty shocked. The driving dynamics are really nice and it looks good on the outside, but I was completely at a loss for why MMI is so beloved. I wanted to look at a prestige level (the highest), but nobody has those in stock to test drive in my area. What I got had a lot of hard plastic, tons of buttons, and an interface that is a better version of iDrive but on a 5.7" screen. You also have to spend a fortune to get the adaptive suspension because it requires you to add a driver assist package to "enable" the ability to add the suspension adjustment. The one I drove didn't even have the different drive modes at all. Some of the nice features like traffic integrated with the navigation is part of a $15/month subscription.
I will give the Q5 a big plus on the transmission. It is really smooth and I pushed it hard a couple times (while simultaneously apologizing to the SA). It seemed to be on the same page with what I wanted it to do the whole time, it was nice. Diesel has a lot of grunt, but it started to lose steam too quickly as you pick up speed....tested by flooring it up a long highway entrance ramp.
Long story short, I would absolutely not buy a Q5 over an MKC, at least for 2015 model year.