You really wouldnt run either of those motors on 6s, not unless you wanted to kill them in a hurry- 1d = 4100kv! and the 1.5d = 2700kv. These are not hvmaxx motors, they dont need to be span that fast to make any kind of power.
The 1512 3d = 1700kv, which is ideal for 6s. What are your specific goals though, as that will ultimately determine the best alround motor.