When comparing Proggy Clean vs Monoid, the Slant community recommends Monoid for most people. In the question“What are the best programming fonts?” Monoid is ranked 19th while Proggy Clean is ranked 42nd. The most important reason people chose Monoid is:
The user can adjust letter-spacing, line-height, and choose alternate characters prior to downloading.
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 Customisable
The user can adjust letter-spacing, line-height, and choose alternate characters prior to downloading.

Pro Novel use of ligatures to display ascii character combinations as symbols
The common expression '!=' is displayed as '≠', '>=' as '≥' *, while maintaining the fixed width double-space that these characters would normally take, so as to maintain text alignment.
- Many others are supported too - see site for details.
Pro Open source
Monoid is open source meaning it's freely available to anyone.
Pro Sharpness
Pro Larger and easier to read with thin condensed letters
Pro Fine without retina
Probably the only one that is.
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 Very narrow
Con No bold-italic style
Monoid doesn't offer a style that is both bold and italic.
