If you're the kind of luser who thinks that GIF is so kewl, these comparisons should get your attention. Please direct anti-PNG, pro-patented-compression comments to your a$$.
Clearly the 24bpp PNG is bigger, about 2.4 times as big as the GIF version, but the 8bpp PNG is smaller than the GIF, which can't be made truecolor since GIF is a rather archaic format that's a nice piece of junk. The truecolor PNG is 30KB, while the 8-bit PNG is more than a full kilobyte smaller than the GIF, at 11.2 and 12.8 KB respectively. And as for the 9.8 KB JPEG, it loses some sharpness, but is smaller than both PNG's and GIF's.
Even on GIF's home turf, PNG edges it out by a third of a kilobyte in this screenshot. At 3.3KB for the PNG and 3.71KB for the GIF, it seems insignificant, but the superiority of the non-patented ZIP compression is obvious here. And the JPEG in this example is the one with obvious degradation. It's also huge at around 20KB.
The verdict: JPEG rules for photos, PNG rules for the rest, and GIF just blows!