The 3DS is worth owning for the same reason the Wii U is: its software library is spearheaded by Nintendo, one of the most consistent and talented developers in the world. There’s no doubt that smartphones have taken a big chunk out of the DS’ user base, but all that proves is that a whole lot of people bought a DS because it was first to what we would now call smartphone-style games. In 2014, many smartphone games are fantastic; very few of the fantastic ones are traditional video games. And if you like traditional video games, you should absolutely own a 3DS.
I love my Wii U. Really looking forward to owning a New Nintendo 3DS.