Not sure what you mean by less efficient and less light.Originally Posted by [b
The rating for wattage is actually a power consumption not light output. So two 2' 20watt tubes burn the same amount of electricity as a single 4' 40 watt tube.
Generally speaking two 2' tubes do put out a little less light than a single 4' tube of the same brand and model. This is simply because a little less surface area inside the tube is lit up if you take a 4' tube and break it into two halves.
Light output which is measured by lumens can vary dramatically and is totally dependent on the bulb. The higher quality daylight bulbs can put out 30% more light than the less expensive coolwhite tubes while using the same amount of electricity.