Did a comet wipe out the dinosaurs?

Around 65 million years ago a giant space object slammed straight into planet earth around the Yucatan peninsula killing 70% of species on our planet. 

Since 1990 scientists have debated what sort of space rock hit planet earth. Scientists know generally how big the explosion would have had to be in order to create the fallout found in drill samples. Based on the size of the explosion and the amount of iridium and osmium deposited at the K-Pg boundary, the most common theory is that the space rock was carbonaceous asteroid about 13 kilometers across. But scientists from Dartmouth College argue that the real culprit was a comet because if moved at the speed that a asteroid couldn't achieve.

So what do you think comet or asteroid?