When comparing Liberation Mono vs Operator Mono, the Slant community recommends Liberation Mono for most people. In the question“What are the best programming fonts?” Liberation Mono is ranked 17th while Operator Mono is ranked 39th. The most important reason people chose Liberation Mono is:
Liberation Mono works well with hinting on high-resolution displays.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Very readable
Liberation Mono works well with hinting on high-resolution displays.
Pro As of 2023: Second Best screen-modern drop-in replacement for MT Courier New
Metric-compatible with Monotype Courier New, dot 0 (zero), modern non-Kettler lowercase l (ell), 660+ glyphs, OFL-1.1 license
Pro Compact line height
Just like Courier New (the metrics of which this font emulates), its line height isn't too big, which results in more lines on the screen, compared to Consolas and several other more popular fonts.

Pro Has Bold typeface
Pro Has a script version
Operator can be used to mix the same font for syntax formatting.
Pro Super readable
Long strings can be read in Operator exceedingly easily. The font just flows nicely, with all the benefits of clarity that provides.
Pro Horizontal width not as wide as other fixed width fonts
You can legibly read everything and get more characters per line.
Pro Adorable italics
Cons
Con Difference between "0" and "O" isn't clear
It can be difficult to tell the difference between the number "0" and the letter "O". However, the Fedora Project has a slightly altered version of Liberation Mono that fixes this with a dotted zero.
Con Liberation fonts are ugly

Con Relatively expensive
At $179, this font is on the more expensive side.
Con Roman style isn’t very appealing
