When comparing Tomorrow Theme vs Leuven, the Slant community recommends Tomorrow Theme for most people. In the question“What are the best color themes for text editors?” Tomorrow Theme is ranked 1st while Leuven is ranked 18th. The most important reason people chose Tomorrow Theme is:
Comes in 5 different variations: Tomorrow, Tomorrow Night, Tomorrow Eighties, Tomorrow Blue and Tomorrow Night Bright.
Question Ranking
Pros
Pro Comes in 5 different variants
Comes in 5 different variations: Tomorrow, Tomorrow Night, Tomorrow Eighties, Tomorrow Blue and Tomorrow Night Bright.
Pro Eases visual processing
Different colors within the same color scheme to quickly distinguish the layout (px, %, ..) and other declaration blocks from the colors (background-color; color); that eases the visual processing, thus increases reading speed, while reading CSS.
Pro Light & dark themes
Dark theme does a good job of contrasting kvps.
Pro There are versions for a lot of applications or it's easy to make your own
There are ready-made packages for Vim, IntelliJ, Emacs, iTerm, etc.
If your app isn't supported the website explains clearly what colors are used, so it should be easy to wrap up your own.
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 Doesn't work with Sublime Text 3
Con May cause eye strain
People with blue-light sensitivity may prefer a dark theme.