I'm picking this quote up from the Dazzler Appreciation thread:
Yeah, your assessment is right: Nocenti's Longshot and CC's Longshot are pretty different. Both have ingenuosness and kindness, but Nocenti's much more bittersweet, sometimes even unintentionally rude, and he seems self-reliant to a certain extent. CC's, on the other hand, seems really as he was born yesterday and he has any concern at all, much like a little child or a pup.
First of all, I'll say I like both of them: I think the mix of these two portrayals makes a richer character, and they're not incompatible.
My lecture: in the beginning of the former miniseries, as well as in the beginning of UXM Annual #10, Longshot suffered a mindwipe. Either the second one was more injurious, or Longshot's mind was already damaged by the previous mindwipe. As a result, during the mini he was savvier and, as time went by (scarcely a week), some of his memories went back, so he turned more focused, responsible and grave, since he had a goal.
When Longshot joined the X-Men, his mind kept totally closed during all those months. As a result, he had a happy-go-lucky personality all the while, and he didn't progress...until his subconscious couldn't bear it any more and it exploided. CC explained this absolutely brilliantly in UXM #248.
Nevertheless, both Longshots share a deep sense of melancholy.
EDIT: I forgot to say that, as far as I know, CC did like Longshot, and he asked for him to be in UXM. Actually, Nocenti said once that CC 'stole' him from her.