Okay, I've got the Nexus and X both open on the Google page now at 50% brightness.
The X screen is a lot brighter at 50% for starters (so I'd probably have it on less than that).
The whites on the Nexus are not even close to being as white as the X, they look a little bit yellow if anything (pentile being exposed?). The colours don't seem much different either though I'd say they are of a marginally higher contrast on the Nexus, but it's fairly negligible. I think for the Google page, the X screen looks nicer, I don't see a problem with the lettering.
As I don't use it, I've just loaded up the CNN site on both and the main block of text down the left isn't really legible on either in portrait. Upon zooming in a little bit the text is marginally crisper on the X but again, it's not something you'd generally notice. The red banner is of a far higher contrast though, so the AMOLED is definitely better there if you prefer more punchy colours.
However, the SLCD advantage comes when you load up a high res image on both for example. I've just loaded up a picture of a tiger and you can see the individual hairs and such far better on the X than the Nexus, where they aren't particularly visible and appear as more of a 'mush'. The other thing here is that the colours seem more realistic, but don't pop like they do on the AMOLED. This could be good or bad, depending on personal preference and what you're viewing.
So, conclusion? Colours/blacks vs accurate colours and sharpness. Same old, same old.
Generally I don't really think about any of this, but I do enjoy a crisp, sharp image.
I could attempt to take pictures with my girlfriends expensive camera but I wouldn't do it justice.
