st vs Terminology
When comparing st vs Terminology, the Slant community recommends st for most people. In the question“What are the best terminal emulators for UNIX-like systems?” st is ranked 8th while Terminology is ranked 9th. The most important reason people chose st is:
st is built to serve as a lightweight terminal emulator. It's very light and doesn't require many resources to run, making it able to run well on older and low-end machines.
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Pros
Pro Low memory usage
st is built to serve as a lightweight terminal emulator. It's very light and doesn't require many resources to run, making it able to run well on older and low-end machines.
Pro Extremely simple architecture
st consists of a single C file that takes seconds to recompile. This also makes it very easy to understand and customize.
Pro 24-bit "True Color" support
st supports color escape sequences for a full 16 million 24-bit color spectrum, instead of the typical 256 colors.
Pro Support for fontconfig
There is full XFT (X Free Type interface library) and fallback font support through fontconfig in st. If your selected font is missing a certain glyph or symbol, but one of your other installed fonts has it, it will be shown.
Pro Copyfree licensing
Copyfree licensing implies that the user has the freedom to copy, use, modify, and distribute what he/she possesses.
Pro Image previews
Handles image previews (e.g. in ranger) way better than other terminal emulators.
Pro Patches are great
The patches on the site are great. Scroll back, hide the mouse, etc.
Pro Minimalist
Hackable and lightweight.
Pro Blazing fast
it is extremely responsive and fast, even on older computers.
Pro Clean
The terminal doesn't have any bloated features nobody uses. It is very minimal and extendable.
Pro Scalable fonts
Font size in Terminology automatically scales according to window size. When you resize the window, so does the text.
Pro Looks smashing
Terminals are often very dull looks wise, not so with terminology.
Pro In-terminal video, picture and thumbnail support
Thumbnails, pictures, and videos can all be rendered in-terminal, based on the directory listing or mouse interactions. For instance, using "ls" on a picture folder will produce a list of thumbnails instead of only the filenames.
Pro Splitable
You can split windows, like in terminator.
Pro Visually customizable
It is very customizable in every aspect of the visual options.

Pro Integrates well with Enlightenment WM
Terminology is part of the Enlightenment WM packages. As such, it integrates really well with Enlightenment and other tools in the package.
Pro Block copy
You can copy text in blocks.
Pro Copyfree licensing
Terminology uses the Simplified BSD License. As it is a copyfree license, it tends to minimize license incompatibilities, legal compliance requirements, and various other complexities that may make it difficult to understand certain licenses.
Cons
Con Configuration requires recompiling
Though recompilation takes seconds, knowledge of C header files is required for customization (though it's pretty easy to do for someone who knows how to edit config files).
Con Text is cut off when resizing windows
In the vanilla build, when reducing windows, lines do not wrap, they are cut off. When the window is made large again, some of the text is missing.
Con Crashes when some characters or colored fonts are displayed
Con No scrollback by default
The best way to perform scrollback is to use a multiplexer (such as tmux, screen, or dvtm) if you want scrollback and reverse-search support.
Con New features means installing patches
Just to get copy/paste support and scrolling, you have to install patches. And it's not that intuitive for a beginner.
Con Internal border/margins
Doesn't support internal margins.
Con Source code edits (aka configs) need to be redone after updating
Con Imperfect fontconfig support for CJK characters
It [st] doesn't seem to use CJK fonts provided by fontconfig while other programs use such fonts.
Con Configuration is sometimes complicated and non-obvious
There's a "Settings" menu for configuration, but more options there would make it easier. Downloading themes and extensions from the official repo would be a big plus.
Con No True-Color support
Not able to display a modern full range of colors, yet.
Con Scrollback is completely nroken
Scrolling back the emulator inserts random lines from other places in the scrollback buffer in between the actuall output lines. Thus it is impossible to see a correct copy of the previous output.
Con No scrollbar
The lack of scrollbar in Terminology makes navigation difficult. But you can use keys for it.
Con Too many bells and whistles
Some people feel that Terminology has too many features that are not suited for a terminal, but for a window manager instead. For instance, viewing thumbnails, watching videos and gifs, and other similarly flashy things just feel like eye candy and should not be part of a terminal emulator.
