Here are my versions done in Color Quantizer:
logo_no_effect.png7254 bytes16 colours
logo_no_effect_8.png 6490 bytes 8 colours
logo_no_effect_6.png 5,851 bytes 6 colours
logo_effect_256.png 24,974 bytes 256 colours
logo_effects_128.png19,274 bytes 128 colours
logo_effects_64.png 14,933 bytes 64 colours
The original effects version contains 4604 unique colours. The 128 colour version looks identical, and only by zooming in dramatically can any differences be discerned. Honestly, any of these versions look visually identical to the full colour originals - I placed all of these on a white canvas, and even when zoomed in I could hardly see any difference at all.
This, my friends, conclusively demonstrates how abysmal Photoshop's PNG export really is: the version with effects is equal in size or even smaller(!) when exported from CQ than the plain version exported in Photoshop.
Photoshop's versions are a minimum four times larger in file size, and in the worst case five times larger in file size.
In CQ the user can choose to limit the range of colours from 16, 32, 64, 128, 256, 512, 1024, 2048, and up to 4096 (or anything in between, and the user can set a lower value than 16 by manually typing the number). Also, a simple quality mask brush allows you to control which areas' quality should be given preference in the reduced colour set. In addition various dithering options and "expert" settings are available to further enhance the quality and reduce the file size.
PNG export in Photoshop is in dire need of a modernization - I would argue it is unusable for current web work. 'nuff said.