When comparing Mustache.js vs pug (Jade), the Slant community recommends pug (Jade) for most people. In the question“What are the best JavaScript templating engines?” pug (Jade) is ranked 1st while Mustache.js is ranked 4th. The most important reason people chose pug (Jade) is:
Jade supports mixins. These not only make your templating job easier but are also super-easy to read.
Specs
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Pros
Pro Clean syntax
Mustache provides you with a clean and easy to understand syntax. Having a syntax that is readable is always a huge plus, since this means easier maintenance and code readability in the future.
Pro Available in lots of languages
Available in a wide variety of languages including Ruby, JavaScript, Python, C++, Scala, Go, Julia, Swift and more. See the full list here.

Pro Lightweight
Mustache is easy to deliver. If you need more features down the road, you can switch to handlebars, which is a superset of Mustache.
Pro Logic-less
By design logic-less templates force you to separate concerns thus helping you avoid future problems with refactoring. It also allow templates to be used with multiple programming languages without changes.
Pro Server side support
Mustache.js has multi-language server side support, which essentially means you can use mustache based templates on languages other than javascript. (like if your server-side was built on Java you could still use Mustache.js)
Pro Popular
This would mean that you'll have a large community to help you out if you run into any problems.
Pro Can be compiled
Mustache templates can be compiled to JS files, so that they can be directly loaded.
Pro Easy to read, powerful mixins
Jade supports mixins. These not only make your templating job easier but are also super-easy to read.
Pro Logic done in JavaScript
The logic in Jade is done with native JavaScript. This means there's less of a learning curve and it'll be easier to get other developers up to speed.
Pro Clean syntax
One of the distinguishing features of Jade is its clean syntax. Elements are created with CSS selector syntax which makes the template consistent with your style sheet and JavaScript element selector library.
Pro Identation reflects nesting
With Jade you can quickly overview the hierarchy of a template.
Pro High performance on the server and client side
Apart from their functionality all template engines need to be efficient in terms of the time they require to render a page. Jade beats most of its competitors in this area, it is highly optimized to deliver good performance on both the server and client ends.
Pro Easy sublayouts using block and extends
By using the extends and block keywords, sublayouts can be made with intuitive syntax.
Pro Preprocessor support
Filters make it easy to embed compiled languages such as coffeescript or markdown directly into the template. A filter will allow you to keep your inline code and content consistent with the rest of your codebase so you can continue using your prefered language with your outputted HTML.
Pro Allows writing inline JavaScript
Jade allows embedding regular JavaScript code directly within the template.
Pro Reuse code in other languages
In addition to JavaScript, you can reuse Jade templates in Scala, PHP, Ruby, Python and Java.
Pro Interactive documentation
There's an interactive documentation available here that allows you to play around with code examples and watch the results in real time.
Pro Compiles to JavaScript
Jade compiles to a JavaScript function that produces the ultimate output. This interim format makes it useful for embedding in conditions where you're trying to save space or decrease processing requirements.
Pro Use Markdown for readable markup
Jade is awesome at templating structural markup, but that's not all Jade is awesome at. It also allows you to use markdown within your template itself which will render to a beautiful HTML page.
Cons
Con Basic tasks are difficult
Mustache js's attempts at making some things simple makes them so easy that they're almost difficult. That is the case with some basic tasks like figuring out how to apply css to shade odd/even rows on your template based content.

Con Bested by Handlebars in many ways
Handlebars being an extension of Mustache bests it in both speed and power. It adds additional features to Mustache which make writing templates easier and faster.
Benchmarks have also shown that Precompiled Handlebars renders in about half the time of Mustache and the rewritten Handlebars (current version) is 5 to 7 times faster than Mustache.
Con Cannot copy/paste examples from the internet
Examples from CSS frameworks like Bootstrap are never utilizing the Pug syntax, which means that you cannot ever copy/paste something to quickly see how it would look or if it works. You would have to convert the HTML to Pug first.
Con Unforgiving in case of indentation errors
The structure is entirely determined by the indentation. That means that indentation errors will ruin the end result, often without an easy way to find the error. Indentation errors are easily introduced by copy-pasting, by rearranging code and by working in a team where not everyone uses the same indentation style. (E.g tabs vs. spaces.)
Con off-side rule templating language not working well with native HTML
plain HTML pages usually can contain very deeply nested structures, whether they are hand-written by web UI designers or generated from popular web design tools or taken from existing HTML templates, which are a nightmare for front-end engineers to convert into Pug templates, where you have to take care of handling the indentation rules and the deeply nested HTML elements, even creating multiple blocks that don't have any meaning in terms of business logic, just to house the HTML elements within bearable amounts of indentations.
Pug templates are nice for Python programmers who don't want to learn HTML to start writing web pages and develop some entire websites personally from the ground up, but for any serious project that involves more than half a dozen people and has separate positions of web UI designers, front-end developers, and back-end engineers, it's much better to choose something more closely compatible with native HTML as the template engine. Pug is simply too alien from native HTML and resembles a lot more like those other off-side rule languages like Python.
Con Bad performance
Bad sintaxe (Short-hand HTML) and bad performance. No streaming or asynchronous calls. https://github.com/mauricionobrega/nodejs-template-benchmark
Con Performance is not great compared to other popular templating engines
