I, too, surprised myself by recently purchasing a 6D (I, not II -- why increase weight and dark noise?) on both lens-selection/lock-in and quickness concerns. I was surprised to find that I loved being able to leave the camera switched on all day in the mountains and draw/shoot/stow in seconds, with 1000+ images on one battery. Barring substantial advancements in sensor/display power consumption, no mirrorless camera can match that property. Furthermore, it is an instrument I can handle/adjust quickly and reliably with gloves on in harsh conditions. For a week at temperatures between -20 and -30 C, the 6D (and iPhones kept warm) operated normally while friends with mirrorless cameras suffered shutdowns.
The three things, from my perspective, that Canon really lacks are 0.5-1 stops of dynamic range in the sensor (SNRs are competitive across all brands, an underappreciated fact), silent electronic shutter, and Sony's incredible array of on-plane focus sensors and focus algorithms (Canon's DPAF may actually compete, if turned loose/optimized further). Sony's eye-detection AF must be a game-changer for portrait photographers.
I'm not at all unhappy with my choice to get the 6d. It's a great camera, and Canon's lenses have all been great. Even though I've always wanted a smaller full frame, any size improvement to the body is negated by the glass unless you get a fixed pancake lens. Good point about mirrorless battery life as well, I don't usually consider it that much since its easy to carry a spare, but I had an eos-m a while back and the battery life was frustrating. Unfortunately, it got trashed in reviews which I think set mirrorless back a bit for canon. Sure the autofocus was garbage, but the 22mm f/2 kit lens for it was amazing (one of the best I've used) and it was the smallest inexpensive camera with the best IQ/$ imo, and it had an aps-c sensor. The rest of the competition was doing m4/3. I remember you could pick up the kit for around $250 or so shortly after it came out.
I'm reasonably convinced that DPAF will probably work out better than Sony's approach in the long run – every photosite essentially doubling as a PDAF sensor seems more future proof than scattering 100+ dedicated PDAF sensors over the chip.
The problem with the latter is that if Canon can develop the software to really exploit DPAF (there's no reason in principle that you couldn't, say, let users chain together an arbitrary number of pixels into selectable AF points placed wherever they want outside of the extreme edges of the sensor), there's no good response with dedicated PDAF, because the more dedicated sensors you place on the chip, the more pixel gaps you create, and the more demosaicing algorithms are forced to infer pixel colours with missing mosaic values. There comes a point where the visual quality will suffer.
This is clearly not due to the nature of mirrorless technology though, so I don't think it's fair to criticize the technology based on that.
Picked up a NEX 5N, 18-55, 55-210, and 16mm for $200AU (~$160US).
Next stop: A6000.
That said, Canon has historically been the winner with their lens selection, and IMO UX. Sony is quickly catching up, or even surpassing them though with e-mount, especially now that more 3rd party lens manufacturers are killing it (Sigma). I also like EVFs more than OVFs since you get a better exposure preview and focus peeking for manual focus. I really, really, really wanted to buy a Sony a7, but I ended up buying a Canon 6d due to lens selection a few years ago (and the Canon beat them on price). I'm a huge fan of mirrorless tech and I'm actually surprised that SLRs are still around.
The camera body is being commoditized. I'm a canon fan and hope they catch up with a full frame mirrorless, my buddy who follows the tech more said he's heard rumors that they are releasing one next year?