Ractive.js vs Vue.js

Ractive fully supports a templating language. To be more precise, views are written with a variant of Mustache, which is also extended to support inline JavaScript expressions. Soon it will be able to support other templating languages.

Ractive has a concept of proxy events, which translate a user action (e.g. a mouseclick) defined via an event directive into an intention (e.g. 'select this option'). This allows you to handle user interaction in a readable, declarative fashion.
on-click='activate'
with arguments:
on-click = 'activate: {{a}}, {{b}}'
It's activate (and not click, nor your function name) that is the name of the handler event that will be fired for any registered handlers created via
ractive.on('activate', your_handler)
ractive.on('activate', your_another_handler)

Of course, Ractive also supports method calls like on-click='toggle(foo)'

Two-way binding can be turned off by those that are concerned it may be a source of bugs.

They have a great interactive tutorial which makes the learning process easy peasy. You will get into it within a couple of minutes.

Instead of relying on the DOM, Ractive implements a virtual DOM from scratch, allowing it to calculate precisely what needs to be patched during the next screen refresh. This is orders of magnitude faster than fiddling with the DOM itself.

Vue can easily be integrated with other front-end libraries. This makes it an extremely versatile tool and it's easy to fix its shortcomings or missing features by just plugging in another library.

Very useful.

Vue.js weighs in at 16kb min+gzip.

Since most of the mainstream server-side rendering implementations are synchronous, they can block the server's event loop when the application is complex.

Vue implements streaming server-side rendering, which allows you to render your component, get a readable stream and directly pipe that to the HTTP response. This allows you to have a responsive server and decreases the time your users have to wait before they get your rendered content.

Although you can build components in JavaScript files, you can also use inline handlebars-like templating in your HTML views where simplicity is often a more sane choice.

Since the template-to-virtual-DOM and compiler can be separated, you can compile the templates in your machine and then deploying only the interpreter which is 12KB minified and gzipped.

You can choose to use either a templating language, or if you feel it's necessary to drop on a lower virtual-dom level, you can use JSX. This is simply done by replacing the template option with a render function.

Or alternatively, you can embed functions inside templates by using the <render> tag.

Starting with Vue 2.0, Vue supports server-side rendering. This helps with SEO a lot, since the views are rendered directly on the server, which are indexed by search engines.