It's not necessarily the size of the nozzle and holes. Those mach injectors have a ton of other work done to them therefore they make a lot of power with the smaller holes.
There is a lot more to injectors, i think Smokem is a great person to ask about that.(search)
That's why some injectors cost a thousand dollars over others of the same size. I guarantee those expensive injectors run, drive, and make power better than cheaper ones.
I have 7x14's and they are more than my current turbos need, and i can airlock my pump at will. If you think smoke is power than by all means get those 6x18's