
This is something that has been emphazised on multiple times. The Wii U and 3DS version will offer the same content on both games except, essentially, they will not. This is what IMGMR writer Seif Mazzene believes the way they should treat the two versions of Smash Bros. 4.
Masahiro Sakurai, Creator and father to the Smash Bros. franchise, wishes to make the fourth installment of Smash Bros. on both 3DS and Wii U and that they can interact with each other in some way. We got the Direct video, the E3 Developer Roundtable and many Interviews, Sakurai is dead set on making the two version very similar, but still unique. Let us evaluate what is the pros and cons of this decision.
Game developer Hideki Kamiya talks about Bayonetta in the Smash Bros. games.

All of the Super Smash Bros. games are incredible, but which one stands as the mightiest of them all and has the best modes?
To me smash brows Melee is my all time favorite. I can't tell you how many hours I played that game between friends and family. When I was a kid, my parents couldn't afford a gaming console so I had to go somewhere that had an arcade like setup with the only difference being instead of arcade cabinets, they had big screen crt TV's and gaming consoles setup. I would go with my friends on special occasions after school or with my family on the weekends.
I would meet and make new friends at that place as we were all gamers and we also brought our game boys and would trade pokemon. I don't think those places exist these days but back then, it was easy to meet like-minded people and have fun for hours.
Well, I’ll add my extremely subjective ranking too. I won’t include the 3DS version as I don’t owned it. I did play it for a few minutes though.
5. Brawl.
4. N64 Smash
3. Ultimate
2. Wiiu Smash
1. Melee

VGChartz's Mark Nielsen: "While the future of Smash Bros. has been uncertain for a while - whether Nintendo will build on Ultimate or bring us a new entry entirely - within all likelihood a new Nintendo system still means something new for Smash Bros. is on the horizon, and that something will almost certainly include new fighters, however many or few. While this might be the gaming article equivalent of putting up Christmas decorations in October, it’s never too early to start speculations when it comes to Smash Bros. before two thirds of everything inevitably gets leaked ahead of time. Keep in mind that this is not a list of predictions for future newcomers, though a few could perhaps fit in that same category, but rather a small list of the characters that in this writer’s humble opinion are overdue an appearance in the gaming crossover to end all crossovers."
If one version is prone to holding back the other then no.
It's gonna have to. For some reason people think Smash on a 3ds is as satisfying as it is on a console.
I think there should be an option. I gave a lot of thought to this same discussion the other day. On the one hand when Smash U comes out you are not going to want to have to unlock everything again, it will feel like a drag. However, if you do get to unlock everything right away than a huge reason to keep playing the game is taken away. Smash is more fun when you know there are things to unlock, things to keep playing for but then again there are some people who will just want to jump into the multiplayer without having to spend the 20 hours unlocking everything. An option would be nice that way it's fair for everyone, if you want to then there it is, if you don't fair enough don't even look at the option.
It depends, the 3DS version definitely held back the Wii u Version, i hope the Wii u version has more content. I would love for Nintendo to introduce the cross save feature, would love to see all the unlock-able characters on wii u version unlocked and still dig the new content if any.
WHERE IS EVENT MODE?