Update: Here’s the 3DS size:

Today’s Smash Bros. Wii U update is rather large, which makes sense given the new content added in. The download clocks in at nearly 1,300 MB. You may experience issues downloading the update and DLC due to heavy traffic, but things should get better as the day progresses!
Coinciding with today’s new Smash Bros. DLC, Nintendo has released updates for both the Wii U and 3DS editions. The two titles are now up to version 1.0.8. After the break, you’ll find the complete patch notes.
Super Smash Bros. for Wii U allows players to connect a 3DS system and use it as a controller. Prior to today, users needed to have a copy of Smash Bros. on 3DS in order to use the feature. An app has now been released with the same functionality, meaning you don’t actually need the game. Pricing is set at $0.99.
The eShop is being absolutely inundated with traffic at the moment, as the new Smash Bros. DLC has released. If you’re experiencing issues, be patient! Normal service should be restored as traffic dies down.
Nintendo’s final trailer for Smash Bros. Wii U/3DS today shows off the new Mii Fighter outfits. Give it a look below.