If you told me that Nintendo opted not to make a 3DS version and only made a Wii U version, I would be absolutely sad. I have wanted a mobile smash brothers for years and we finally got it. Sure it was held back by Nintendo's tech but imo it did a great job and will still be relevant after Smash Wii U simply because of the convenience. I might be busy this weekend to play Smash at my house with friends, but **** our lunch breaks sure get intense at work!
The Wii U one looks to blow out the 3DS one by a lot in terms of presentation and features, but...The Wii U is newer, stronger, and more capable than the 3DS, so you should expect nothing less. Imagine if they made it like Playstation All Stars where they were essentially mirrored copies of the game, it would feel even more arbitrary.
That gamecube controller and those HD graphics will sell you literally anything, huh? Look at it objectively: Smash Wii U is full of really awful looking game modes and extra bells and whistles you'll use all of twice before noticing how stupid they are. Wow! More stages! Except 95% of them will be awful, riddled with annoying hazards and be useful only for another different looking Final Destination. Even Gaur Plains has somehow been made worse with the addition of Metal Face.
3DS version is the superior version. If I want to play against someone in Smash, I don't have to say "hey come over to my place later and we'll play Smash", I can just whip the 3DS out and we can play. It's the same reason that Pokemon is successful. Honestly, there shouldn't even be a Wii U version. Mewtwo will just end up being like $2.99 on the eShop a week after he goes live anyway.
I wouldn't really call this post "objective"...It's actually a rather pessimistic opinion post to me.
Those modes may be superfluous to you, but as a party fighter/casual experience, it's doing a lot new things that the previous installments did not do.
And to proclaim that "there shouldn't be a Wii U version" is quite incendiary. To ignore Smash's console roots and only stick it to a (relative to the Wii U) inferior system doesn't make sense. Even in local play, lag is possible. Now we can play on huge television screens, in HD, with a controller of our choice. You are trivializing the improved visual experience and comfort as being "sold on HD".
I also have a feeling some of these stages will have the ability to have "boss mode" turned off, but that is just speculation on my part.
Considering the only thing you are losing out on the Wii U version is portability, I am highly surprised you feel the 3DS version is superior to the 3DS version.