Both. I plan on investing a lot more time into the Wii U version though.

There will probably be some kind of promotion. " If you have 3DS version buy Wii U for half price" or something.
Wii U for me, as I think I will have a hard time controlling it on the 3dS.

Wii U day 1 but the 3DS i want to hear how it plays on the original 3DS

I am still not sure but I think in the end I will buy both versions. I am really looking forward to the Wii U version. But the 3DS version comes earlier and most of my friends only own a 3DS not a Wii U. I still hope there will be some great modes exclusive for the Wii U version. But the graphics look great.

Both, likely. If the Wii U version had come out first, I might've skipped the 3DS one, but since it's the other way around I'll probably be too tempted and get the 'light' (imo) version, then the 'real' (in my eyes) version on Wii U.

http://smashbros-miiverse.com/pic-of-the-day/2014-07-25

This shows there's clear interaction between the two - one reason I'll be getting both.

Smash only makes sense to me as big screen mayhem, and I rarely play it on my own anyway, so I'm only bothering with the Wii U version.

Im getting both

I love both consoles and cant skip my favorite game of all time on both of them. The 3ds game is also coming first and even if i want to, I cant wait 2 more month for the WiiU release. Cant skip the WiiU for local multiplayer of course.

Wii U.
For me, its a system seller for Wii U, whose library is pretty well founded.
Obviously, 3DS library is larger, but if KH3DS, Pokemon, and Kirby didn't make me buy it Smash 3DS certainly won't.