Sonic: Lost World's multiplayer on Wii U is local only, while the 3DS version features online, four-player versus racing, Producer Takashi Iizuka tells Nintendo World Report. Lost World on Wii U has cooperative and versus multiplayer modes, both couch-based, while Iizuka mentions only the four-player, online versus mode for 3DS.
"In cooperative play, Sonic will be using the Wii U GamePad and someone can be supporting Sonic in co-op with the Wii Remote," Iizuka says. "In versus mode, one player will be playing on the TV screen and the other player will be racing using the GamePad so you don't have to have split screen. You both have your own screen and can race each other."
These details build on previous Lost World multiplayer announcements from Sega, which note that the 3DS version will have "exclusive Special Stages and Color Powers unique to Nintendo 3DS."