I'm fairly new to android and have tried nova, apex, and go launcher. I didn't find a big benefit over touchwiz. The only thing i really liked was being able to re-size and get more app's on one page, but other than that i wasn't impressed. As far as speed goes, you can change window and transition animation settings in touchwiz to make it just as fast. What am i missing?
On touch wiz you can't have more than 4 apps in the one dock. On the other launchers you can have multiple docks and have multiple apps in the dock and even one by one widgets in the dock. There are also gestures for the apps in the dock.
Home screen you can have available wall paper, change icons for apps and add effects for when you go through different screens. Add double tap and gestures for one and two fingers that you can assign to shortcuts, apps, and I think widgets and things like recent apps or Google search.
You can also change the way you scroll in the app drawer, change the transparency, And change groups like widgets, apps, and whatever.
Probably a few more features I didn't mention. Although some of these are . Only in the paid version. I hope j cleared some stuff up for you