I'm aware, but as some studies [0], and my body, shows, their effects are not similar. Black tea doesn't make me tense and causes heart palpitations for me. Instead, I keep my calm and being able to focus.

I don't reduce coffee because of caffeine, but because it affects my appetite, makes me tense when I drink too much, and causes heart palpitations and makes me uncomfortable. Black tea doesn't do any of that.

[0]: http://apjcn.nhri.org.tw/server/apjcn/17/s1/167.pdf