When comparing Railscast vs Leuven, the Slant community recommends Railscast for most people. In the question“What are the best color themes for text editors?” Railscast is ranked 15th while Leuven is ranked 22nd. The most important reason people chose Railscast is:
Obviously Railscast was designed for Ruby. It's easy to see where your code blocks begin and end.
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Pros
Pro Syntax highlighting makes it easy to see block indentations in Ruby code
Obviously Railscast was designed for Ruby. It's easy to see where your code blocks begin and end.
Pro Helpful for people with astigmatism
People with astigmatism prefer the bright white background since the extra light causes your pupils to contract, which makes your focus sharper.
Pro Helpful for people with deuteranomaly
Leuven is a high-contrast theme preferring blue hues to red ones which makes it easier for people with deuteranomaly (most common form of red-green blindness) to distinguish different syntactical elements.
Cons
Con May cause eye strain
People with blue-light sensitivity may prefer a dark theme.