I think there was a lot more evidence against OJ; he also had the history of abuse toward Nicole. KC had no history of abuse or violence toward, or even neglect of, Caylee; Caylee by all appearances was her healthy, happy normal self until something happened suddenly after June 15. There's quite a bit of evidence that Caylee was murdered, but no evidence showing only KC could be the murderer (at least that we've seen yet).
It's funny you should bring OJ up, early in this case I remember saying to friends, "Can you believe the things the media is actually saying about this young mother? Back when OJ was a suspect, no one said ANYTHING like the kinds of things they are saying about her. In her case, it's like a free for all!" "Is it because the media know that she's too poor to sue?"
In the case of OJ, there were the videos of the beaten up Nicole (from the domestic abuse in the months or years preceding the murder, the audios of her phone calls to 911, etc), but no one on the air said, "OJ is such a narcissist, he's obviously a psychopath and murderer!" or went on at length discussing his supposed personality flaws, what a party boy he was, or whatever.
With this young suspect/defendant we've heard defamatory comments repeated over and over daily in the media for more than 8 months. The theory about her being guilty and remorseless, a psychopath and narcissist, has been repeated so many times in the media it has taken on a life of its own, people often quote this theory as if it is fact.
The other day on NG they kept showing the pictures from KC's 21st birthday (a year before Caylee's disappearance) and claiming that it was pictures of her out partying it up after killing her child! The program's mental health expert went on in detail about how these pictures showed her doing a dance of joy about murdering her little girl. Unbelievable. Why pictures of KC urinating and chewing with her mouth open or clowning around and making a mean or crazy face for the camera? Why no discussion in the media at all regarding the other people who were around KC and Caylee in the timeframe corresponding to the disappearance, why none of their facebook and photobucket pictures shown or discussed in the media, etc? The bias in the media has been extreme. I have the impression some people's parents' lawyers stepped in quickly to stop discussion of their children and to block their pictures being used in the tabloid media, also. My impression only.