The Wii U GamePad is a portable console.
The Wii U GamePad’s screen is 6.2 inches diagonal, more than an inch larger than the PS Vita’s, and when it comes to ergonomics — in particular the GamePad’s proper full-sized thumbsticks — the GamePad smokes Sony’s handheld. Yes, you have to be pretty much in the same room as the Wii U for GamePad-play to work properly, but I use the feature enough at this point (with a burgeoning family invading my game space) that not having the option to snap off and step away from the TV feels regressive and even prohibitive at this point.
Nintendo has the eShop. Sony and Microsoft have nada.
The PS4 plays PS4 games and the Xbox One plays Xbox One games — that’s it at launch. The Wii U? Wii U games of course, but also the entire Wii library (over 1,000 and counting), as well as NES and Super NES classics via the Virtual Console, from Super Metroid to F-Zero and Earthbound to Super Mario Bros. 3.
Yes, Sony’s promised streaming game support in 2014 to fold in backward compatibility, but the service has some pretty serious caveats: visual artifacts and total picture degradation if your Internet connection wavers, plus you have to be online, by definition, to play.
