Amazon A7s info claim A7s has 15.3 stops of DR!

[Erik Wittbusch]

8 bit images contain more than enough color information to be de-logged and graded. May not have the same latitude as higher bit depth images, but as long as your smart about your exposures and color balance you shouldn't have a problem.

We just need to wait, how the slog footage of the A7s will really look.
The slog2, that I know from the FS700 is not worth it until you record 10bit or more via the CG Odyssey7Q. It's just too noisy if you delog the footage by lifting up the shadows and mids that much.
In the end it's a matter of taste. I will use cinegammas in 8bit over log-footage any day.

 

[LeoGrey]

Perhaps you haven't exposed your image correctly if your needing to lift shadow and mid values that much. Protecting your highlights is one thing, making the right call as to what is important inside of the scene is another.

I have shot day/night scenarios with the fs700 and never had a problem grading the 8 bit footage. The same can also be said with the f3, c100, c300 and the 1dc

 

[nyvz]

Yeah I haven't found slog2 to perform much differently than cinegammas if you expose them the same. I usually 'overexpose' slog2 around 1-2stops and there it has similar noise performance to cine4 but with much nicer color and much more natural tonal gradations once you restore saturation and/or contrast in post.