Different tools for different jobs.
I also own a 5D3, but I prefer to use the 6D in low-light situations because it has better AF and IQ.
I'm primarily a wedding photographer, so my typical subjects are usually walking to/from the alter in dark churches or dancing at dark reception venues. However, here's a 6D shot of my friend's dog (1/2000, f/2.8, ISO 800).
./showthread.php?p=17584332&i=i175279599
forum: Photography Industry News
Nice shot!
I had a 6D as a second body for weddings, but preferred the AF tracking on the 5DIII, as I never found its AF sensitivity to be an issue...even when I shot dark churches at night with no flash. If AF sensitivity is your priority, the a7s will AF to -4 EV across the frame.
Different strokes for different folks, but I find more value in the 5DIII's AF tracking, which works really well at tracking focus across the frame...very useful for keeping up with the bridal parties moving down aisles, dancing at the reception etc. Doable with the 6D, but involves a lot of panning.
Speaking of AF tracking, here's a video showing how well the a6000 can track motion:
https://www.youtube.com/watch?v=q-8I502JTMU![]()
Once Sony brings this AF to a full frame camera, my 5DIII is gone 



He told me to drink my coffee and leave, free coffee yeah


