850 vs 860 as boot drive

Near-zero difference in boot times. For standard Windows applications read times are HEAVILY used so the 850 would have a SLIGHT edge. The real world difference is pretty much completely unnoticeable. Get whichever one is cheaper.
 
The pc is basically running all the time and I put it in sleep mode when not in usage so boot time won’t make much difference it’s programs and such my games and adobe files will be on separate drives so the 850/860 is just os and programs
 


Still whatever is cheaper, while charts may show some small differences you will not notice the difference in real world use.
http://ssd.userbenchmark.com/Compare/Samsung-860-Evo-250GB-vs-Samsung-850-Evo-250GB/3949vs2977

Now if you were talking about a 960 EVO NVMe SSD or 850 EVO then the choice is obvious.
http://ssd.userbenchmark.com/Compare/Samsung-960-Evo-NVMe-PCIe-M2-250GB-vs-Samsung-850-Evo-250GB/m200373vs2977


I own the 850 EVO 500gb and it works well for the programs that are on the drive as well as bootup.