what is a faster boot drive?

The difference is minimal and also tied to your motherboard.
I.E: The motherboard will have a bigger impact on boot time than either one of those ssds.
 
Solution


In those 'specs', what specifically points to the 950 and 'boot faster'?
Yes, overall it is 'faster' than the 850. In some numbers, by quite a lot.

But what leads you to determine 'faster boot'?
 


All I said was "faster" overall, I'm not sure which of those specs will contribute to a "faster boot".
 
FWIW, I have used both.
My son needed my 850 PRO, so I replaced it with a 950 PRO.
I could tell no difference. If anything, the 950 PRO was slower because of longer initialization of the motherboard.

And, I rarely boot anyway.
If you use sleep to ram, it takes3 seconds to sleep or wake.