Those who own an original 3DS will not be able to play Hyrule Warriors Legends in stereoscopic 3D, according to producer Yosuke Hayashi. In a translated interview with 4Gamer, Hayashi revealed that in order for Hyrule Warriors Legends to have as many enemies on screen as the Wii U version, the 3D functionality on the original 3DS version had to be sacrificed because it was too taxing on the system. Presumably because of the better specifications of the New Nintendo 3DS and 3DS XL, the game will be playable in stereoscopic 3D on those systems.

Source: IGN