When comparing ERB vs Slim, the Slant community recommends Slim for most people. In the question“What are the best Ruby templating languages?” Slim is ranked 1st while ERB is ranked 2nd. The most important reason people chose Slim is:
Slim's documentation is well organized and detailed, every concept is thoroughly explained and it is very helpful for both advanced users and beginners.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Comes with Ruby
Since ERB is included with Ruby out of the box, there is no additional installation and setup required. The fact that it's included by default in Ruby, a lot of projects use it.
Pro HTML with embedded Ruby
ERB is a way to embed Ruby into plain HTML, which means there is no need to learn a new syntax for HTML. This makes ERB fast to learn, and a great option to use on projects that have multiple developers/designers.
Pro Familiar even for developers with no Ruby experience
ERB's interpolated tags are very familiar to developers who have worked with PHP, ASP or JSP, even though they may not have any prior experience with Ruby.
Pro Maintained by Ruby on Rails developers
Due to Ruby on Rails (RoR) use of ERB, the developers of RoR will continue to maintain ERB, guaranteeing project health.
Pro Best Performance
It has the best performance of all of ruby templates, although it wasn't designed for productivity as HAML or SLIM.
Pro Well organized and thorough documentation
Slim's documentation is well organized and detailed, every concept is thoroughly explained and it is very helpful for both advanced users and beginners.
Pro A good starting point
Slim is minimal and that is a good thing if you want to start from there. It can be easily extended and even supports popular packages that are used in Laravel (like Illuminate\Database (eloquent)) for example.
Pro REST based
REST fans will love the REST based architecture.
Pro Supports tie-ins for Rack-like middleware
Rack is an interface used in Ruby frameworks used to group and order modules, which most of the time are Ruby classes, and specify between them.
Slim uses a simple concept for it's middleware. By wrapping HTTP requests and responses it unifies the middleware into a single method call.
Pro Useful classes
Contains classes for managing requests, responses, cookies, logging, views, HTTP caching, and more.
Pro Flexible
Slim doesn't demand that you stick to a fixed folder structure. As long as you load Slim the right way you can do anything from there the way you like it.
Pro Extremely lightweight
Paired with swoole it's a micro service powerhouse.
Pro Open source
The Slim Framework is open source and is released under the MIT public license
Pro Extremely customizable
You can add any dependency, package or class that you want to use as a contained dependency.
Pro Supports Php 5.3 and PHP 7
Pro Makes it easy to understand the way some abstract functions and classes are built
In Django most things are abstracted, you just call some function or class without knowing how they were built, but with Slim, you end up understanding the way some abstract functions and classes are built.
Pro Hooks for executing code at different points in its life-cycle
Slim supports code hooks for executing functions at different points in time during the application's lifecycle.
Cons
Con Verbose
Since ERB uses HTML syntax with Ruby logic inside it can get a little verbose like HTML files usually do.
Con Very little consistency among different versions
There have been quite some changes that break the compatibility between Slim 2 and Slim 3. Even if you learned how to work with the Slim 2, you will find that Slim 3 requires re-training.
Con Dependency injection is too weak
It is not really dependency injection, but just a configurable container.
Con Needs strong bases to create dependencies
The dependency container schema of Slim is one of the biggest PROS and CONS of the framework. It is true that this schema brings so much flexibility to add anything, but another thing that is true is that you need to have strong bases of patterns, and an extensive knowledge of your libraries to convert it into a Slim dependency.
Con Too minimal
While it's true that Slim is a microframework, it's still too minimal. When used for throwaway projects or simple prototypes, it's perfect. But in the long run, it becomes less and less useful and you end up in implementing a full custom framework in trying to tackle all the missing features.