Not round for round, I do however think that a full magazine of .380 has more accululative stopping power than the six rounds of a .38 special revolver.
The Colt Mustang Plus II (a 380 with an extended grip and extended magazine) holds seven rounds. A standard Colt Mustang only holds six. I don't know about other brands. Are there 380's with double stacked magazines like you see on many 9mm guns, or possibly larger 380's that hold more rounds? I always associated 380's with "small in size". Easy to carry, but limited in both firepower and stopping power.