Keep in mind that I'm a student with two priorities: (a) to keep a healthy body with MINIMAL EFFORT needed for a GIVEN level of desired health and (b) to increase my focus and attention span. Now the latter is somewhat desirable when it comes to my desire to drink tea, but I'm also willing to sacrifice some caffeine for health benefits.
So when it comes to some mixture of healthfulness AND caffeine, which brand of green tea is most healthful? Gunpowder, mate lemon, etc etc etc? Which green teas have caffeine levels that are most similar to those of black tea?