"The caffiene in both acts as a stimulant; if used in the proper amount and timed right, it is highly beneficial to training."
Caffeine dehydrates you. This is not something that you want to do in any amount prior to training. Drink water or gatorade. Caffeine also raises the heart rate and can affect blood pressure. Also not things that you want to do prior to your work out.
Sure, you want a workout that raises your heart rate. But pumping it up unnaturally is not a good idea.
In moderate amounts tea and coffee will not be harmful to a healthy person. But misuse of a stimulant, even a legal one, will cause health problems.