Since burnallgifs.org is offline here is a description why PNG is better than GIF:
unambiguous pronunciation (ooo, baby!)
multiple CRCs so that file integrity can be checked without viewing
ultra-clever magic signature that can detect the most common types of file corruption
better compression than GIF, typically 5% to 25% (but often 40% or 50% better on tiny images)
non-patented (you betcha!), completely lossless compression
majorly gnarly two-dimensional interlacing scheme
1-, 2-, 4- and 8-bit palette support (like GIF)
1-, 2-, 4-, 8- and 16-bit grayscale support
8- and 16-bit-per-sample (that is, 24- and 48-bit) truecolor support
full alpha transparency in 8- and 16-bit modes, not just simple on-off transparency like GIF
``palette-alpha'' mode, effectively transforming normal RGB palette into RGBA
gamma correction for cross-platform ``brightness'' control
color correction for cross-platform, precision color
both compressed and uncompressed text chunks for copyright and other info
full Year 2000 (Y2K) support, and then some (good for at least 63 millenia! yowza!)
free and complete reference implementation with full source code
http://www.libpng.org/pub/png/