Stop press...JKogas says something positive about karate...
"..or potential (karate has advantage)."
I must admit when I first looked at this thread I had to think in terms of all things being equal. That is why I voted for karate hands.
The argument for boxing is centered around the idea that the majority of training is more realistic in terms of contact. However it is not that realistic to practice punching (no matter how hard) with your hands all neatly wrapped up and protected by big cushions.
I personally know of a couple of boxers that have smashed their hands to pieces in real fights because of poor alignment and fist formation. Something that is taught very early on in any decent karate club.