The Coffee Junkie's Guide to Caffeine Addiction
nymag.com
nymag.com
(For the record, green tea has a small amount of caffeine.)
Tea, particularly green, also has Theanine (http://en.wikipedia.org/wiki/Theanine), which smooths out the caffeine jitters. I'm pretty sure theanine is a big part of why green tea feels subjectively different in effect from coffee, even when drinking enough to counterbalance the lower caffeine content.
1. Easier to keep intake from growing out of control.
2. Easier to keep caffeine levels steady since the pills take less time and effort than making more coffee and the dosage is very consistent. No unexpected crashes.
3. Teeth/mouth.