No they're not not the same as they each contain the things needed to compile stuff for their respective platforms but once you subscribed for the dev section (it's free, just do it!) you can download everything from there.Ur welcome.
A friend showed me this image. Same should be done about 3ds unity version. Their both SDK(s) should be backed up (since i'm not in their dev program, idk if SDK is the same for both Wii U and 3DS or they are different).
Ps4 and PSV unity were leaked with their respective SDKs too.
Idk if same occurred with Xbox One.