Actually, it seems that the 3DS Version will have less content due to space. Yes, it has Smash Run and likely has Classic, Adventure, and All-Star, along with the Local/Online Multiplayer and the normal things like events and Home Run Contest, but the Wii U version has My Music, doesn't require Multiple Copies/Systems for Local Multiplayer, and may have its exclusive be Stage Builder. Its likely we'll find out anything Wii U exclusive in the Pics of the Day following the release of the Nintendo 3DS version.
My Wii U collection is actually growing close to my 3DS collection, with Mario Kart 8, Super Mario 3D World, Donkey Kong Country: Tropical Freeze, New Super Luigi U, Game & Wario, The Legend of Zelda: Wink Waker HD, Monster Hunter 3 Ultimate, Resident Evil Revelations, and Batman: Arkham City - Armored Edition.
Not saying that you'd like those games or even that they'd interest you..but I just wanted to show I was the opposite of you in a way I guess lol
I'm looking forward to Hyrule Warriors and The Legend of Zelda U, along with Super Smash Bros. for Wii U.
As for being more competitive internationally? I don't know, I've never seen a handheld game become competitive before, aside from maybe Mario Kart DS & 7. I think both will be competitive in a way, since the Wii U version would likely be preferred for Tournaments, since a physical connection will be available (connecting several Wireless Things in the same room can be a veritable hell on Earth for Tournament Supervisors), though I think that, overall, both will have a very competitive online community. This is true for Japan as well, since I see a great many Japanese users online in Mario Kart 8 as well, nearly every time I'm online, actually..though mostly at night since that's daytime over there.