Well everyone has different tastes. To me the PW rendering is better because it has a heavier weight (bolder, darker) and the anti-aliasing is stronger. I think in real world use where the fonts are rendered much smaller than they appear here on our large monitors, that thinner but sharper Touch rendering becomes more difficult to see and appears to my eyes as a lighter shade of text. When I compare my PW and Touch side by side with light level 0 on the PW, then the PW rendering is indeed better for my eyes, though only marginally. As I crank up the light level the PW rendering is still better but it seems to suffer more degradation the higher the light level.
The thing I liked most about the K4S was the ability to add our own font choice without jailbreaking. I was able to find a heavier Caecilia on FontPark.net that had a normal text weight about half way between the Kindle Caecilia's normal and bold text. If that makes sense. Reading where all the text has been bolded was a bit difficult, but reading where the normal text was semi-bold seamed just right. Substituting a custom font worked a lot better than modifying each book to make it display all bold text.