In order of purchase:
3DS
+3D effect
+great library of games
+pedometer
+backwards compatible
+Swapnote (before it got discontinued)
-poor Circle Pad Pro support (I love that peripheral!)
-shitty web browser
-poor media capabilities
-relatively weak hardware
-uncomfortable without a seperately purchased "grip'
Vita
+backwards compatible
+great controls
+PS4 remote play
+great graphics
+good browser
-less than stellar software support
-3G is absolutely useless
-expensive memory cards (I've been maxed out forever)
-not really comfortable
-ashamed to play with it in public
Wii U
+Best browser of all consoles!
+great games/backwards compatible
+awesome controller does everything
+Miiverse
+free online
-Poor 3rd party support
-lost a lot of the Wii's features (photo channel, etc.)
-screws up simple online basics (ie:messaging, game invites)
-can't turn off the controller during certain functions (ie: Netflix)
-childish presentation at every turn
Playstation 4
+best streaming video (WWE, Hulu, Netflix)
+Awesome controller
+most powerful
+Remote play with Vita
+Great 3rd party support
-no PS3 support
-interface feels pretty generic/bland
-lack of media support found on PS3
-flimsy headset
-can't control TV like the other two consoles
Xbox One
+Great 3rd party support
+"Snap" feature is a gift from up above
+Voice control is awesome (when it works)
+TV feature is awesome
+My personal fav controller
-Kinect is under-utilized at the moment
-gesture controls suck sometimes
-Voice control sucks (when it doesn't work)
-No backwards compatibility with X360
-Loss of many 360 features
