It is interesting how differently we perceive that.
For me, SX series has MUCH better panel buttons. On PSR-S they are kinda wobbly when pressing. On PSR-SX however, they are firm and pressing them feels much more solid. It's an improvement I noticed immediately when I tried in local store. And that fact alone gave me an impression of more "serious" keyboard.
Now, I can't really say sticks more on new black buttons -despite the fact that dust is just more visible on black surface. But in my experience, dirt that collects over the time by pressing them a lot, is more visible on white ones (bottom row on PSR-S). Anyway, I see dust/dirt as a minor issue here.
New post arose while I write that.. about black keys are less visible in low light. Is true! But there's always "some" light.. right?

And the obvious question: is it worth to "upgrade" from PSR-S to PSR-SX? It made sense to me (mostly because of touch screen) and I have no doubts about my decision. Is true: I can't really do "more" on PSR-SX than on PSR-S... but many things I can do easier now.
As said, we percive things differently and have different priorities.. so I respect and try to understand everyone's opinion.
Just my 2cents
