I don´t know either Swish or Contexts, but both looks like a window manager. Can you tell me, why do you need both?
I use Spectacle, but sometimes it feels like I need some more flexible.
Edit: Nevermind, my bad. Contexts is a switcher, not a manager
Swish is for when you want to quickly organise windows using gestures. It’s the gestures that sold me on it. As for Contexts, it is only an app switcher but really useful if use multiple windows of the same application. Fast jumping between them by the name of the application or content of the title or anything else fuzzily is incredible. Do note that all of these make sense if you are a heavy keyboard user.