I think the face lost a bit readability in arachne's version, and maybe there's too much noise on the limbs and midriff. Maybe it's apples an oranges. I like the hands though, and the chest works well.
I kinda like the small feet. It gives the design simplicity in its overall shape (upside down teardrop \/ rather than dull parallel lines ||). See Mr. Incredible from
The Incredibles.
All robots are not metal. See Asimo or "The Robots" (animated film). The problem with shiny metal is that you get values which bounce a lot, making it hard to describe details. This is what happened to arachne's face. When you're also working within limitations such as these with so few pixels and colors to work with, I think you risk ending up with too much noise.
Slightly related, Paradroid for the C64. Scroll down a bit. They share a lot of parts and use flipping, I think.
http://homepages.tesco.net/~parsonsp/html/paradroid.html