Does a growth light actually do anything? Im using a 40 watt flourescent bulb for my VFT, which i heard was enough. What does a Growth Light do that a regular light cant?
It completely depends on the specifications of the light. How many lumens and what color temperature (kelvin) are you asking about comparing? There are many kinds of 40 watt light bulbs. The wattage of the light doesn't give you any indication of the things that are most important when trying to choose good lighting for plants. It simply tells you how much energy the light is going to use and how it will affect your electric bill.