I used to be a caffeine pill person. Would get up at 4:30, have a caffeine pill and a glass of water, ride my bike for a couple hours, go to work. In that case, I wanted caffeine first and liquid later (throughout my ride) so I wouldn't have to make a "rest stop".
I kept up the caffeine pill habit after I stopped doing those rides (social life after work made going to bed at 8:30 a little untenable), but ran out and switched back to coffee. Coffee really gives you some extras that mere caffeine doesn't, I just feel a little "warmer" after a good cup of coffee. Also, all those papers you read about coffee being good for you are coffee, not necessarily caffeine. So if you want those benefits, I recommend the actual thing.
I have some friends who drink energy drinks just for the caffeine ("I hate the taste") and to that demographic I recommend caffeine pills wholeheartedly. If you don't like the taste of caffeinated beverages, don't drink them.
