Why will the 3DS version of smash be any less competitive than the Wii U version?
It's the exact same game.
You could argue that tournaments are easier to set up with the DS version too. No venue or TV's required.
It's not the exact same game at all. Different stages, different modes, low resolution, lower-res textures, single controller, no local multiplayer with 1 disc (will require more than 1 game card, you bet.) Music will be severely impacted, with only 2 tracks per stage, Nintendo probably wants to fit it on a 2 GB card for the physical release tops (4 GB exist with a tiny number of titles but are more expensive and rare.) Amiibos, if you desire them, will require a separate device to use, since the 3DS does not come built-in with NFC capabilities
. Tourney's would be worse with a 2.4 GHz ad hoc Wi-Fi card implementation, not to mention interference from any other 2.4 GHz devices. As someone with an OG 3DS myself, the controls and size of the screen aren't going to be too hot either... Smash is way better on a big TV at a higher resolution/image quality than on a tiny 240p screen, and even if you think that's opinion,
the default options for black outlines and your eyes will tell you different.
3DS wasn't designed for Smash like it wasn't designed for 2 extra shoulder buttons or a second analog stick.
The game CAN'T be the same game because the architecture of the 3DS and Wii U is completely different. One is ARM and one is PowerPC. Even the assets that have been reused (i.e. character models) have been heavily cut down to work on the older and completely different 3DS hardware. It is not the same game at all, unlike say, a Pokemon X and Y.
Fewer stages and modes is a definite possibility, that's conjecture, but we'll see. I'd bet my avatar on it.
Advantage-wise, load times will be quicker, given the solid-state memory, less RAM used and less RAM to fill. Also, input lag will be very low given the built-in screen. The wait from the frame buffer to the image appearing on screen will be near instant.
