I'm probably one of the biggest boosters of Nintendo's 3DS out there. I've put hundreds of hours in on my beloved, battered handheld, and I even play with the 3D slider all the way up. That's why this is the last thing I ever expected to say: I've played Super Smash Bros. on the 3DS and Wii U, and I recommend waiting for the Wii U version to come out.
When I played a demo version of the game on a 3DS XL, I was disappointed in how small and squashed it all felt. For once, the close-ups that we've seen of the game via screenshots look better than the real thing. My poor Pikachu was a little yellow blob, lacking in the personality that he displays on the big screen or even in the mainstream Pokemon games. There's just too much screen real estate that needs to be shown to play Smash, and the individual character models suffer.
This isn't just a problem of looks or personality. It will be more difficult to read opponents on the small screen, and more difficult to keep track of the chaos in multiplayer fights, especially when items are turned on. Playing with nearby friends isn't as much fun if you're staring at separate 3DS screens instead of the same big-screen TV, either.
Online multiplayer features are another reason to wait for the Wii U version. Smash Bros. on 3DS should be all right for quick pick-up games, but playing with specific people requires wrestling with the Friend Code system. I expect the Miiverse (where exchanging Friend Codes is forbidden) will be a wasteland of bans when Smash 3DS comes out, and the entire North American 3DS multiplayer scene will probably be much quieter after the Wii U version launches.
Finally, we're starting to get an idea of just how many unlockable items are packed into the new Smash Bros. games. We'll be unlocking characters, trophies, custom moves, and even outfits for our Mii Fighters. At least the trophies will differ between the two versions, but do you really want to grind for unlockable items twice?
I know that many fans are foaming at the mouth to get their hands on Smash, any Smash, and to start practicing with the new characters and moves, but I'd still urge people to wait. Smash Bros. is more that just a game series, it's one of those rare franchises that isn't simply released. A new Smash Bros. game is an event. It's going to be a lot more exciting to crack the cover on the game for the first time with the big-screen Wii U version. If you know that's the version you'd rather have anyway, why settle for the lesser version in the meantime?
Smash Bros. belongs on the big screen. If you're planning to buy the Wii U version at all, skip the 3DS version and wait to be bathed in the glow of the Wii U's gorgeous graphics, stronger multiplayer connectivity, and greater sense of excitement. It'll be worth it in the end.