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Whenever possible, use one lamp with a bright bulb instead of two lamps with less bright bulbs. The light output efficiency of higher wattage bulbs is greater, so less electricity is used overall.
The light output of a light bulb is measured in lumens. The electricity usage is measured in watts. The efficiency of a light bulb is measured in lumens of light produced divided by the watts of electricity used.
For example, a typical 25-watt light bulb produces only 210 lumens of light. A 100-watt light bulb produces 1600 lumens of light. It requires about eight 25-watt bulbs (200 total watts of electricity used) to produce as much light as one 100-watt bulb. Therefore, a 100-watt bulb is twice as efficient as a 25-watt bulb.
For comparison, a 60-watt bulb produces 820 lumens of light and a 75 watt bulb produces 1170 lumens of light. Don't be confused by three-way bulbs. They are actually two lower wattage elements inside one bulb. A true 150-watt (single level) bulb will produce more light than a 150-watt three-way bulb.