There is no release date for the Wii U version although people are saying November 21st. 2.Depends on how much space on your Wii U you have. 3.The only exclusives are some stages, and a gamemode exclusive to each, 3ds has Smash run, and the Wii U has Tower of Smash *Tower of Smash was a leak that is believed to be real so no confirmations on that.*
Skial
Chance
Meowrisa
Its Sm4sh. 1: November / December. 2: Its your choice, I like physical. 3: Smash Run for 3DS and Free Music for Wii U. Plus each version has different stages.