FWIW, over the weekend building out my tiki bar, I had yet another situation where the M12 bottomed itself out and the M18 pushed through. In this case I was using the Kreg HD meant for 2x lumber (larger hole, larger bit, larger coated screws) and the M12 took at least three plunges (often more) while the M18 never required more than to (2 is my minimum to clear chips anyway).
So while the M12 can do the task, if you've got a lot of work to do that adds up quickly in terms of time lost to the smaller tool.