The main diff b/w the 2 IMO
Backbone is more customizeable and suited for larger apps.
Backbone stays out of the DOM for the most part so it's a little bit more manageable long term.
KO does great w/ smaller multi-page apps that need a lot of complex forms etc, like you said.
The thing is, you can make Backbone have the 2 way binding style of Knockout with something like https://github.com/NYTimes/backbone.stickit, it just takes more setup. But, it also might be worth the time and effor to set up.
Knockout does what it does and does it really well, whereas Backbone has many more possibilities.
Bottom line, they're both great frameworks, just different approaches to both.
Thanks for the explanation, makes a lot of sense, I have to take another look into KO, it's just there is not enough hours in the day to do everything I need to :(
Be well