When comparing Proggy Clean vs Google Roboto Mono, the Slant community recommends Google Roboto Mono for most people. In the question“What are the best programming fonts?” Google Roboto Mono is ranked 26th while Proggy Clean is ranked 42nd. The most important reason people chose Google Roboto Mono is:
Roboto Mono has a very clean and beautiful design.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro The easiest to read
All characters are completely readable in the smallest size.
Perfectly usable in terminal and code editors in 12px text size.
Pro Hipster among hipsters
Even hipsters will marvel at this font, praising you as the new hipster lord. It is best at around 19px (tested on Mac). Overall, it has better readability than many default fonts.
Pro Looks really beautiful
Roboto Mono has a very clean and beautiful design.
Pro Clean and legible
Roboto Mono is crystal clear which makes it a good choice for reading code without your eyes getting tired.
Pro The right thickness
It's neither too thin, too fat, nor too condensed. Roboto Mono is just right.
Pro All variants available
Both bold and italics look great in Roboto Mono.
Pro Distinctive uppercase vs lowercase characters
The median line is placed relatively low. This makes reading mix-cased words (eg. hashes) easier.
Pro Readable, elegant and cute
It's very readable, elegant and cute. Almost indistinguishable with SF Mono at small point sizes. It looks great even as a display font.
Pro Makes for an excellent font for terminal
Roboto Mono looks particularly well on iterm2.
Pro Released under the lenient Apache License
Pro Powerline Patched version works well
This is the only font that works well and looks good with agnoster theme and powerline for bash/zsh.

Pro Looks great on HiDPI
Looks good at 14pt and lower, but looks great at 20pt and higher, making it an excellent font for higher resolutions
Cons

Con Pixelated
This is, of course, intentional; but it can be hard to look at compared to other smooth mono-space fonts.
Con Smallest font sizes hard to read
Fonts less than 11pt start to fail readability tests. 9pt specifically has an additional issue where brackets don't align.
Con Not really good in all font-sizes
Completely clean pixels, no anti-aliasing so its best viewed in (n*12) pixel size.
Bold font-weight is not really good because of small padding between them.

Con Curly braces aren't very distinctive
The curly braces are too close to parentheses, which can harm readability for programming.
Con Not recognized as monospace font
Windows does not recognize the font as monospaced. Cannot be used as terminal font.
Con Sublime Text doesn't show italic version
font face "Roboto Mono" has different widths for italic characters, disabling to prevent text reflow
