I really like this visualization of the difference between Deja Vu Sans Mono and Apple Menlo:

(Credit to Jesse Burgheimer)

I decided to take a stab at programmatically generating a similar comparison for all the fonts I’ve been looking at. Here’s the Mathematica code.

(Click for full size version)

It was then easy to generate this for every pair of fonts:

I went through them all and picked out the ones I thought were most interesting:

If you’re interested in seeing the results for every pair, you can download them all.