Oh? I really liked Xbox 360's "blades" dashboard UI. It was quite fast, and was quite simple. On every screen, there's a clear indication of what your controller buttons do, making it really quick to get around in. Some video of the dashboard in use: https://www.youtube.com/watch?v=1P5gTvXct30
I dunno what UI the 360 had by the time I got one (maybe after the One was out? Or just a little before) but 90% of every screen is ads.
The blades UI was quick, but I remember so many slow loads when pressing the Xbox button and pulling up the system menu.
But I do agree, the blades UI design-wise was pretty good and achieved far more information density than the crossbar PlayStation UI. But when in-game I wouldn't describe any of the UI as speedy.