Also, many people don't realize, or talk about it, but caffeine actually has health benefits as well!

Here's the list of benefits from Wikipedia:

• High long-term consumption is associated with a lower risk of cardiovascular disease and diabetes.
• Research is beginning to suggest that caffeine minimizes the cognitive decline associated with aging.
• Caffeine increases levels of neurotransmitters such as norepinephrine, acetylcholine, dopamine, serotonin, epinephrine and glutamate.
• Acetylcholine is associated with attention, concentration, learning, and memory but there is no conclusive evidence yet that caffeine has any effect on memory and cognitive function.
• Low doses of caffeine show increased alertness and decreased fatigue.
• Caffeine has been shown to increase the metabolic rate.
• Caffeine may reduce the risk of developing cancer and produce a delay in the average onset of cancer.
• Caffeine may be associated with a reduced risk of Parkinson’s disease.
• Caffeine may lower the risk of developing type 2 diabetes.
• Caffeine may reduce certain kind of hepatic cancers.
  

Green tea contains less caffeine than most black teas and coffee. Plus green tea has many health benefits. I say go with the green tea!