Best overall: Sony Alpha a7R II

The Sony a7R II wins this group for many reasons: it is arguably the most innovative, most improved, and houses the most features of any camera in this category. 399 PDAF points offer the largest frame coverage and truly challenge full-frame DSLR AF. We were in disbelief at the incredibly high AF hit rates we observed across multiple shoots, so we baselined the system against DSLRs in a slew of continuous AF tests to find that, sure enough, the a7R II challenges some of the best DSLRs, even in low light. Continuous Eye AF is a boon for candids of even moving subjects, and better-than-DSLR AF accuracy ensures critical focus for shallow depth-of-field applications. Many of these AF benefits disruptively carry over to 3rd party lenses when using electronic adapters, an industry first. 

In-body stabilization and electronic shutters allow you to worry less about handheld and mirror or shutter-induced shake, a clear benefit over high-resolution DSLRs. Internal 4K recording is a first for this segment, as well as BSI technology on a full-frame camera, which gives the a7R II class-leading low light image quality and continues Sony's tradition of high dynamic range Raw imaging. The a7R II overcomes inherent issues of many DSLRs and especially the shortcomings of its predecessor, and the sum total of innovations and features help get the camera out of the way, allowing you to focus on image-making. Switch back to a DSLR and you may find yourself searching for that Eye AF button or wondering if you should microadjust that prime or why your video looks so soft or jittery (no IBIS). While we still have concerns over ergonomics, and mirrorless cameras still have shortcomings for sports photography, one cannot deny the sheer photography-accelerating technical prowess of the a7R II. When we say “Sony wins at cameras,” for 2015, we really mean it.

Also consider: Nikon D750

We originally had the Nikon D810 picked as the 'Also consider,' but ultimately the D750, with its much more affordable price tag, better low light AF and excellent all-round performance, took its place. It's worth noting that unless you need the extra resolution of the D810, its deeper buffer, or chart-topping dynamic range, the D750 is the sensible buy in our minds. And while the Sony a7R II has taken mirrorless to infinity and beyond in terms of overall capability, there are still plenty of good reasons to prefer a DSLR over a mirrorless camera: better battery life, shorter startup times, no viewfinder lag, no stop-motion playback of images as opposed to a live feed during bursts, better ergonomics, etc.

For those that still want to do things the old fashioned way, the highly refined D750 still remains the top choice in this class, especially if you want to shoot sports or action (though its buffer is limited in Raw shooting). The sensor performance, while not as high of resolution as the Canons, still outpaces them in terms of low light performance and dynamic range. We also have found the 3D tracking AF system to be simpler yet more robust than Canon's equivalent (iTR) in most shooting cases, meaning you can trust the camera to follow your subject no matter where it moves to in the frame. It's worth noting though that mirror and shutter-induced shock can introduce some softness at longer focal lengths and slower shutter speeds when pairing the D750 with Nikon's 'VR' lenses.