Hrrrm...Itachi is definately cool. He's got that badass attitude thinly veiled by an extremely calm demeanor. But he's not fooling anyone. He'll fucking kill you and you know it. That's cool in my book. But when I think cool, the idea of heading out to a basement with some friends, some beers, guitars, and kung fu movies come to mind. Among the group of people I'd want to enjoy those things with, I'd rather Kakashi be in it. Laid back, decent sense of humor, and last but not least, far less likely to stick a kunai in my throat if for some reason he got pissed at me.
Now, if I were some of the girls I've been running into lately....I'd think Itachi was cooler. Mainly because cool would be associated with who I want to have sex with more, and that would be the guy who'se more likely to beat me halfway to death.