Between the pills and tea I guess whatever made you take it would be better but with pills you are not very assured at all of quality, contaminants, concentration, etc. although I suspect most of them are descent. But it's the problem you face with any concentrated herb...you can get concetrated contaminants. For instance lead contamination has been fround in a number of green tea pills. Of course tea is going to be very variable but for the most part when you buy tea you are assured of getting tea, whereas when you buy pills you are not assured of much anything
The amount of polyphenols to caffeine can widely vary among different pills depending on the standardiztion and stuff. So you can end up with a 500 mg. pill wth 5 grams of caffeine and another 100 mg pill with 25 grams of caffeine both with completely different polyphenolic amounts (if they meet the label claims that is) so check the amounts if you get pills.