When comparing Fira Mono vs Input Mono, the Slant community recommends Input Mono for most people. In the question“What are the best programming fonts?” Input Mono is ranked 4th while Fira Mono is ranked 51st. The most important reason people chose Input Mono is:
Input can be configured online with preview: width, weight, line height, and alternate letterforms.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Looks great and is easy on eyes
Almost looks like Source Code pro and works great with Intelli J where Source Code Pro renders all junk on one of the primary IDE.
Very good for people who read code through out the day.
Pro Extremely readable
You can look at the code for hours and hours. The height between lines and the spacing is perfect.
Pro Offers better performance in some Emacs builds
This font is used by some Emacs users on Mac OS X in order to get better performance.
Pro Highly configurable
Input can be configured online with preview: width, weight, line height, and alternate letterforms.
Pro Available in Mono, Sans, and Serif
There are a couple advantages to using a proportionally spaced font in code: comfort of reading, ease of spotting typos, and better differentiation between different kinds of code with font styles. Fontbureau dedicated an entire page to this topic. Unfortunately, a lot of text editors only support monospaced fonts.
Pro Clear distinctions between similar characters
The font is easy to read, has a clear distinction between similar character types, is very customizable with weight and line height. Free for personal/unpublished usage. You can customize the font how you like it on their site before downloading it to use.
In some fonts, it's difficult to distinguish between similar characters such as i/L/1, or o/zero, or m/rn. This font does an incredible job at making all of these examples clearly identifiable.
Pro Clear on low resolution and retina display
The code stays clear on low resolution and retina display with the same font option.
Pro Large, obvious punctuation
Pro Light, Extra-Light, Thin weights
The designer advises using a lighter weight for light-on-dark color schemes.
Pro Serif font is remarkably readable
Pro Condensed and Compressed Thin saves a lot of space
When using the condensed or compressed version with the thin typeface, you gain a lot of screen space and it's still extremely readable for all day coding.
Cons
Con Large line height
Compared to other options, Fira has a high line height, which reduces the number of lines you can see on screen at one time.
Con Closed source
Although font designers need to make money too, open source model is preferred.
Con No ligatures
This can be a pro or con depending on who you ask, but it would be nice to have the option.
Con In VS2017 this font does not work and displayed as "Courier New"
Con Hard to distinguish "8" from "B" at low sizes
This often impacts upon designers working with hexadecimal numbers. Many fonts address this by either changing the x-height for numerals, making "8" more of an hourglass shape, or making the "B" cap smaller. At 10 pt, there's less than three pixels of a difference (anti-aliased).
Con Gets the job done, but not rounded enough to be pleasant/easy on the eyes
Con Bold 5 and 6 are too similar
Con Decimal digits can blend together in Mono variant
A lot of decimal digits have a similar form, 2's can sometimes look like 8's and so forth, which makes long strings of digits hard to read. I find other fonts like Consolas's digits more legible even at smaller sizes.
In the proportional variants this is less a problem.
Con Easy to confuse lowercase "i" with "1" if you're not used to it
The dot is so close to the body that they fuse, and with the serif on top it looks like the cap of the letter "1". When you put them side by side it's easy to see which one is which, but if you see a code that reads "a+=i" you're going to read that it increments a by 1.
Con The tilde is indistinguishable from a dash
Tilde is basically indistinguishable from a dash, unless you blow the size up huge. The curves in the tilde are too shallow.