At first sight they don't seem to be "clones" of each other, like it happened with the Nethack wiki vs the Nethack wikia, so there's no need for us to decide what's the canonical source of information. Just choose the reference that you find more accurate, or complete, or up to date as you normally would.
I'll point out that, while Wikia may have bad rap with its aggressive advertisement schemes, it does have a free content license, unlike Curse's Terraria (and Minecraft) Wiki:
You agree to not engage in the use, copying, or distribution of any of the Content other than expressly permitted herein, including any use, copying, or distribution of User Submissions of third parties obtained through the Websites for any commercial purposes. If you download or print a copy of the Content for personal use, you must retain all copyright, trademark and other proprietary notices contained therein.
Curse Terms of Service
It should be noted that we've been upgraded to CC-BY-SA 3.0, so we're now compatible with Wikipedia, Wikia and similarly licensed content. Attribution requirements remain, obviously.