There are tradeoffs in everything we do in life. Everything is relative to your situation. There are no absolutes.
Let's revisit a conversation our team recently had in HipChat. It was the ultimate debate of pros vs cons, and at one point it turned a little bit emotional.
There are already a bunch of debates documented on the web. Just a simple Google search gives you enough to make your head spin: HAML vs ERB vs SLIM in terms of render speed, Haml vs erb, Fashion Runway: ERb vs. Haml, and so on. You get the point.
But, what about the arguments we were making?
We shouldn't be afraid of it.
I sensed a little fear from our team, so I had to say that. Our team isn't exclusively developers. Most of us know our way around HTML & CSS, and since we use ERB most of the time, everyone at least knows what it looks like. But, like anything else, we shouldn't avoid something because we're afraid of it. It's usually good to step out of your comfort zone.
We have an existing code base.
We have an application where we used ERB exclusively. Why should we try to make the switch to HAML? To me, it's a waste of time and a poor decision that wouldn't provide many benefits. While our code would suddenly be cleaner and a little more beautiful in HAML, we'd waste precious hours converting ERB to HAML. We have so many other important things to do, why waste that time on something so pointless in this case?
I can write ugly code in any language.
One of the common arguments for HAML is that it's clean and beautiful. While I agree that a language that depends on whitespace forces you to indent and keep things organized, I guarantee that I can write ugly code in HAML as well. Look what I found: Haml Sucks for Content
That doesn't look pretty and organized to me. If you use a tool like HAML in the wrong way, you'll end up something that looks terrible. Like Chris says in his post about why Haml Sucks for Content:
Haml’s use of CSS syntax for IDs and class names should make it very clear: The markup you write in Haml is intended to be styled by your stylesheets. Conversely, content does not usually have specific styling - it is styled by tags.
It's important to realize that your situation is completely different than everyone else out there. If you're starting a brand new application and you plan on experimenting with some new tools, you can afford to use HAML (and it's usually a good idea to learn something new). But what if you need to stand up an application in a week? Use what you know.
There are plenty of reasons to not use HAML. Maybe, you don't have time to learn it. Maybe, you have some junior developers on your team that only know ERB. Maybe, you have a personal preference against HAML.
It's all relative. You don't need to use HAML. ERB can do all the same things. They are just different tools for the same job.