Caffeine is good. Plenty of benefits from studies, even some claiming it's protective of the heart etc. Personally I wouldn't take preworkout powders b/c the dosing is hard to get right. A 200mg tab of caffeine is a 200mg tab of caffeine. How much caffeine is in a scoop of preworkout powder? There's two sources of variance, how much powder is in the scoop and how uniformly the powder is combined at the factory. I'd just stick to tabs, cheap, convenient and exact.