So I have to correct myself on my previous thoughts on my refurbished 350. I couldn't tell much of a difference with my 505 before, but after installing PRS+ on both of them and updating my font to a slab serif font in bold with nice thick strokes, and also after getting and *loving* my 950, I realize that I had somewhat of a misconception about Pearl screens. (Or maybe not, but based on my limited experience, here are my conclusions.) I was looking more for a lighter background. it seems the improvement was mostly in the darker font. I didn't notice it very well with my initial comparisons because I compared in bright light. In low light, the contrast is definitely better on the 350 screen compared to the 505, and once I updated to a font that is actually good for e-ink (shame, Sony. the default font is HORRIBLE on e-ink. I didn't even realize what I was missing.. basically the difference is night and day) I can tell how much darker the font is on 350/950 vs 505.
But, with decent light, and when I'm not comparing directly, to be honest my 505 still has pretty darn good clear print and I can happily read on it. So it makes me feel a little guilty to have bought the 950.. I love it, but my 505 still works so well (although the battery life is definitely shorter than it used to be). (Doesn't help that apparently my stupid dental insurance doesn't think a teeth deep clean should be covered, and I just got a bill for $540 after thinking that the clean would be covered.. wtf.)
I do like the 350, and I see that it is very sharp and even readable at the XS size (with a suitably bold and good font for e-ink, anyways), but after trying my 950 and 350 extensively, I prefer to read on my 950 despite the lower weight of the 350. A 650 might have been the perfect compromise, but I like the Wi-Fi of my 950 and the larger screen. If I can find a cheap 650 I'll buy it to compare, but I think I am going to return my 350 and keep the 950.
Also, forget what I said about excessive flashing. The page turns are definitely faster than my 505, and I felt they were "darker" maybe because of the increased contrast. the sony 505 sort of pauses a half-second and then fades into the next page, where as the 350 does it faster and maybe darker, but I see that it's not a defect, it was just that I was so used to my 505.
I think I would hold on to the 350 if it were pink, just because it would be too cute and maybe I could throw it in my bag. But as of now I think I will return the 350 to sony. It is a lovely device, but I prefer 6 inch or larger screens, I think.