I mean.......yeah. I'm unclear how this was a revolation to you. It would be like me saying "$20 is more useful than this rock I found!"
Depends on if you need to know what "qualia" means, or if you need to know what a "Parisian doobjob" is.
I've always felt that Urban Dictionary and a Dictionary are situationally useful. I would've never known what 'eepy' meant if I used a normal dictionary (honestly, I guessed what it meant just to test myself), which is always late to add new slang words. All the same Urban Dictionary would never be useful for finding the meaning of a well established word.
Then again Wikitionary has both, so just use that for everything (including scrabble if you wanna get chaotic)