Coffee and Cappuccino both have caffeine levels of around 95mg. I’d say cappuccino is stronger than coffee because it contains higher amounts of carbohydrates, fat and sugar. You also taste more sweetness with a cappucino, so you subconsciously think to yourself, "this must be giving me more energy".
A medium to small cup of regular drip coffee typically has around 95 milligrams (mg) of caffeine in a typical 8-ounce cup. The conversion rate for Cappuccino is much higher as this drink can contain anywhere from 135-500 mg per shot (~1oz). Medium cups correspond to about 135 mgs while larger cups come in at over 500 mgs as noted