You can probably shave off another .2W by disabling the HDMI and LEDs, but an RPi3 at load will probably be at 4+W from the wall.
At the same time, you're comparing the power consumption of lets say 10 whole RPis/platforms to the consumption of a single processor. Stick that processor in a platform (laptop), and it's going to use much more than 40W.
Like you said, you get a lot more with the laptop, but given your benchmark (10x difference), my guess is that 10x RPis would still be more power efficient than a laptop with a 6700HQ at that specific task.
At the same time, you're comparing the power consumption of lets say 10 whole RPis/platforms to the consumption of a single processor. Stick that processor in a platform (laptop), and it's going to use much more than 40W.
Like you said, you get a lot more with the laptop, but given your benchmark (10x difference), my guess is that 10x RPis would still be more power efficient than a laptop with a 6700HQ at that specific task.