Sonic Lost World runs in Native 720p Upscaled to 1080p on Wii U, 3DS Version runs at 30fps

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60fps is much more important than 1080p. 720p to 1080p isn't a big difference unless you sit too close or have a ginormous screen. 30fps to 60fps on a fast paced game, however, is much more noticeable.
Sonic Team made the right choice here.