i probably didn't state it very well.
If you run small wattage grows, you do not get as good light penetration as with a higher wattage lamp. here are 2 examples.
grower one uses a 400W hps for flowering the other uses 150s. the optimal area of illumination for the 400 watt lamp is much greater ~ it can be between 1 foot and four feet away (this is theory, i know with a cool tube yada yada lol). with the 150s it needs to be between 5 inches and 2 feet.
the upshot is you want to keep the plant a size that can be illuminated efficiently by your equipment.
BTW i've been doing this since '83~i now run VERY small, i used to grow the big uns ha ha