Caffeination....
Looks like differences in caffeine content between espresso and other brewing methods are not significantly different on a per serving basis.
"By means of comparison, a 7 oz cup of coffee has the following caffeine (mg) amounts, according to Bunker and McWilliams in J. Am. Diet. 74:28-32, 1979:
Drip 115-175
Espresso 100mg of caffeine
1 serving (1.5-2oz)
Brewed 80-135
Instant 65-100
Decaf, brewed 3-4
Decaf, instant 2-3
Tea, iced (12 ozs.) 70
Tea, brewed, imported 60
Tea, brewed, U.S. 40
Tea, instant 30
Mate 25-150mg
The variability in the amount of caffeine in a cup of coffee or tea is relatively large even if prepared by the same person using the same equipment and ingredients day after day."