Non-Headless Web E2E Testing tools for KnockoutJS

I have a project with some months into development and now we're looking into tools to do end-to-end tests for the GUI part.

The project is an SPA, using knockoutJS, Jquery, RequireJS, w2ui, etc + WebAPI 2.0 on the server side.

We want something NOT headless so that we can see what's going on under the hood and also we want to be able to target different browsers.

I've been doing some research and I've found the following tools:

• Protractor
  • Pros: Supported by google, huge community
  • Cons: Targets mainly AngularJS
• Selenium
  • Pros: GUI to help crate the tests. Oldest and most tested. Multi programming language
  • Cons: Hard to use (as reported by many users)
• NightwatchJS
  • Pros: Simplification of the Selenium's WebDriver. Good Comunity.
  • Cons: Has its own testing framework. Not much information available on how to use with knockout
• Sahi
  • Pros: Looks quite simple.
  • Cons: Free version isn't full featured.
• FuncUnit/WebDriverIO
  • Pros: they just look like nice possibilities.
  • Cons: The community around them isn't that big.

My question is: what's the best tool to choose under these circumstances (not headless, several browsers, knockoutJS, project already in the middle) ?

Thank you so much for all the incoming feedback,

Regards