In the Kepler days, and earlier, Quadro cards would support double precision at a much faster rate than their consumer counterparts. That's not the case anymore; double precision is only found on GP100/GV100 and nowhere else.
Quadro cards additionally tend to have twice as much VRAM as their consumer counterparts, as professionals may be dealing with projects that can saturate it. I think this VRAM may also have ECC capability, though I'm not sure.
The most important aspect of Quadros, however, is the extra performance in professional applications that they provide. This increase is artificial, but what you're really buying when you buy a Quadro is access to NVIDIA's certified drivers that perform immensely better in professional applications than the Geforce drivers.
This chart illustrates it quite nicely:
https://www.servethehome.com/nvidia-quadro-p6000-high-end-workstation-graphics-card-review/
The most interesting point on that chart is the Quadro K5200, which is a GK110 (Kepler) based Quadro, cut down further than even the GTX 780, and it's smashing GTX 1080s and Titan Blacks. That's the increase you get from the certified drivers.