Alternatives
I have usually compared Malline against ERB, but there are also other alternatives to ERB and Malline.
Markaby
Markaby is the reason Malline was developed. Markaby is very similar to Malline, or more like Malline have stolen some good ideas from Markaby. =)
Unfortunately Markaby had it's problems with my projects, and I couldn't use it in production. However, I don't know the current state of that project.
XmlMarkup
Builder::XmlMarkup comes with Ruby on Rails, and the basic "block" syntax have derived from there.
Haml Haiku
Haiku is a template language, that aims to be beautiful. The project seems interesting, and if you are evaluating different template systems, don't miss this one. I haven't personally ever used it, because I don't like the idea of totally new template language. But that's my problem!
Erector is also worth a mention as an alternative.