Many might say that the second site is a recognized educational institution and that would be why the second one is most likely more credible, but it's quite more than that. The biggest issue is that the first one is a Wikia. Those kinds of sites tend to be very editable and changeable by anyone in many ways. Pages can be completely different or disappear the next day. Even though there might be some sort of moderation, the same does not happen in the second site. And even if the information is wrong, it will not be suddenly changing.
It’s a site where anyone can modify the content.