Marko vs Polymer

Marko consistently outperforms other alternatives in code benchmarks, both on rendering speed and compilation time.

Custom tags provide a simple mechanism for embedding more complex components into a template by extending the HTML grammar with support for new tags. For example:

<div>
    <say-hello name="World"/>
</div>

Custom tags are easy to create since they just map to a JavaScript "renderer" function as shown below:

module.exports = function sayHelloRenderer(input, out) {
    out.write('Hello ' + input.name + '!');
}

Custom tags support nested content:

<fancy-overlay title="My Title">
    This will be the body content of the overlay
</fancy-overlay>

Custom tags can also have parent/child relationships to support more complex use cases such a "tabs" component with nested "tab" components:

<fancy-tabs>
    <fancy-tabs:tab label="Home">
        Content for Home
    </fancy-tabs:tab>
    <fancy-tabs:tab label="Profile">
        Content for Profile
    </fancy-tabs:tab>
    <fancy-tabs:tab label="Messages">
        Content for Messages
    </fancy-tabs:tab>
</fancy-tabs>

Streaming allows progressive HTML rendering and reduces time to first byte.

Marko supports both server-side and client-side rendering.

Marko Widgets allows UI components (rendering + behavior) to be built using Marko.

Avoids ugly globals and "named" templates.

var template = require('./template.marko');
var html = template.renderSync({name: 'Frank'});

Marko makes additional asynchronous calls after the view rendering has begun.

Easy Integration with Express and Node

The documentation is extensive and very helpful. It also contains several sample applications which are very useful.

JavaScript expressions can be executed inside the templates.

Marko has a HTML-like syntax which should be easy to read and understand for everyone who has even minimal experience in web development.

It is easy to get up to speed and understand what is going on in a very short period of time.

Marko's compiled templates are usually very small, as proven by benchmarks.

To prevent regressions, Marko includes a full suite of tests. The testing harness renders a collection of templates and does an exact string comparison to make sure that the tests rendered exactly as expected. There are also API tests, and negative tests to make sure that errors are reported in a friendly way.

To run tests:
git clone https://github.com/marko-js/marko
cd marko
npm install
npm test

Error messages come in an easy to read and friendly format, with valid stack traces and file formats of the file(s) which brought the error(s).

The Concise syntax type lets you write Marko with a Jade-like indentation based syntax, and the Mixed mode lets you combine in regular HTML-style syntax.

Marko's development community is rather small compared to other frameworks but community is well mannered and active. You can chat with the core development team using gitter.im

It provides a base component.

HTML markup as it can be a non-string.

It provides Flex layout components.

CSS can be applied far more comfortably than React.

The presence od specialized debugging tools are advertised by competitors. The all features of web components are natively supported by browser embedded development tools.

The router is embedded into CLI for project creation and covers as web as Progressive web app, also fused with Polymer layouts out of the box. The shop template for CLI has a complete solution including the routing.

Full app stack from data tier to routing, progressive web app, responsive layouts makes no need to seek outside of Polymer ecosystem for application features.

In addition to waste set of mature web components in Polymer Elements along with Vaadin Elements there are thousands of web components in the wild comparable to jQuery plugins set.

Polymer guides you as with tools (cli, build environment, app templates,..) as with complimentary documentation on all phases of app development from creation of app as progresive web app to production deployment instructions.

As Polymer is standards based, the whole community around those standards also helping in documentation and support.

Web Components are a collection of specifications released by W3C as a way to reduce the complexity of web apps by creating reusable components. Browser support is currently poor for web components, however Polymer is developed to make web components compatible with modern browsers.

The Polymer APIs are split on application layers and follow standards on all possible ways: Web Components, CSS variables, async API via Promises and so on.