We already knew about a large gulf between the internal storage of the Wii U's Basic and Deluxe models: 8 GB versus 32 GB. But Nintendo has revealed another wrinkle to the decision. After accounting for the firmware and the potentially large size of full digital games, space is probably going to run out rather quickly, especially for Basic users.
A new Nintendo Direct (via Kotaku) breaks down the details. As a starting point, the Basic has 7.2 GB of memory after formatting, compared to 29 GB for the Deluxe. But setting up (account data, etc) will take up 4.2 GB on its own, leaving the Basic at 3 GB of usable memory, and the Deluxe at 25 GB.
You can probably see the problem emerging. A game like New Super Mario U is doable on either system, taking up only a slight 2 GB of space. But at 3.2 GB, Nintendo Land won't fit on the Basic at all. That case is particularly problematic since the Basic is the set that doesn't come with Nintendo Land on a disc anyway. The Wii U disc capacity is up to 25 GB, which means that if a game takes full advantage of the disc storage, buying it digitally would use up all the space on your Deluxe.
The good news is you can use USB hard drives. If you have a USB flash drive, it's probably best to use it for storage of games you aren't actively playing. Plug-in hard drives will work fine, but a portable hard drive that needs a power source will require a Y-cable.
Simple, right? This all sounds a bit too confusing for the casual market that made the Wii a smash success. If managing storage space on the console is unwieldy, it might be hard for Nintendo to get them back.