When comparing EJS vs Marko, the Slant community recommends EJS for most people. In the question“What are the best JavaScript templating engines?” EJS is ranked 6th while Marko is ranked 10th. The most important reason people chose EJS is:
EJS uses all the JS jargon and logic, so if you're proficient in JS, you can use EJS right away.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Complete JavaScript logic
EJS uses all the JS jargon and logic, so if you're proficient in JS, you can use EJS right away.
Pro Same language before and after rendering
Your html/text remains pretty much the same before and after rendering. EJS filters out and performs its functions on any occurrences of its own <%= %>
tags in your template.
Pro Lightning-fast to learn
EJS introduces fairly small amount of new syntax that one has to learn to become fully proficient. The syntax itself is easy to comprehend for anyone who is even somewhat familiar with JavaScript and CSS.
Pro Consistently scores rather well in benchmarks
According to some benchmark tests, EJS is way faster than Jade or Haml.
Pro Powerful error handling
EJS has a really smart error handling mechanism built right into it. It points out to you, the line numbers on which an error has occurred, so that you don't end up looking through the whole template file wasting your time in searching for bugs.
Pro Extremely fast
Marko consistently outperforms other alternatives in code benchmarks, both on rendering speed and compilation time.
Pro Custom tags
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>
Pro Streaming
Streaming allows progressive HTML rendering and reduces time to first byte.
Pro Server-side rendering
Marko supports both server-side and client-side rendering.
Pro Marko Widgets
Marko Widgets allows UI components (rendering + behavior) to be built using Marko.
Pro Compiled templates are readable CommonJS modules
Avoids ugly globals and "named" templates.
var template = require('./template.marko');
var html = template.renderSync({name: 'Frank'});
Pro Asynchronous rendering
Marko makes additional asynchronous calls after the view rendering has begun.
Pro Lightweight runtime (~4 KB gzip)
Pro Easy to integrate with express.js
Easy Integration with Express and Node
Pro Documentation is well maintained and helpful
The documentation is extensive and very helpful. It also contains several sample applications which are very useful.
Pro Allows JavaScript expressions
JavaScript expressions can be executed inside the templates.
Pro Simple and readable syntax
Marko has a HTML-like syntax which should be easy to read and understand for everyone who has even minimal experience in web development.
Pro Short learning curve
It is easy to get up to speed and understand what is going on in a very short period of time.
Pro Small compiled templates
Marko's compiled templates are usually very small, as proven by benchmarks.
Pro Lots of tests
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
Pro Friendly compile-time error messages
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).

Pro Concise and Mixed syntax
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.
Pro Server and client logic can easily be expressed within the same template
Pro Has a very active and interactive community
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
Cons
Con No support for block by default
EJS has no support for the block
functionality which allows you to reuse pieces of templates across different files. Although it can be added to EJS through a third-party library.

Con Cryptic syntax
Much more difficult to read, especially for designer/HTML people who don't write JavaScript.
Con If you want to get the full experience you have to use NodeJS
To use markojs's most popular feature: SSR although you can use any language based server as a backend. It is rather complicated.
Con Very opinionated and not customizable enough
Some custom use cases are not possible. For example, trying to build an AMP page using Marko can be very challenging (special style tag requirements are hard to work with, also, Marko by default inserts a script tag into the rendered output html which is invalid in AMP and needs to be manually removed, etc..)
