This is the best comparison I've seen:
http://www.product-reviews.net/2014/01/29/ps-vita-slim-oled-vs-lcd-before-uk-release/
The Vita1000 seems to have much better contrast and black levels whereas the LCD looks muted in comparison.
http://www.vg247.com/2013/09/12/photo-comparison-of-oled-vita-screen-and-the-new-lcd-emerges/
in this one the lcd looks better to me.
the OLED looks too dark in some dark scenes and i have heard of black blotch and screen burn issues, although for screen burn you have to be keeping a static image for a long time and I have always bought plasma but I know OLED especially early versions of it is far worse than plasma for image retention.
screen burn is non existent on plasma these days but still an issue for OLED.
the OLED looks cooler (bluer) and oversaturated, the LCD looks like a slight green tinge but with slightly accurate more normal colours.
there is no definitive answer to which is better but to what you prefer imo.
I would really need to see both in front of me tbh, as with videos it depends how the camera is set up a lot it could have a bias towards one than the other.
also I heard OLED is bad for sun glare as well.
if I had to choose i would probably opt for the newer one because of battery life, bigger buttons and it's lighter and slimmer.
screen wise OLED has better blacks but I think it's a oversaturated picture on the whole, the LCD is more accurate but a bit washed out, not as deep as the OLED. I would probably prefer the OLED screen tbh if it wasn't so dark on dark scenes and have blotch issues.
it's not a easy choice to make between them imo, both have their good sides and downsides. if they had improved the OLED screen in the second version obviously that would have been the best of both worlds.
i really need to see both of them in real life imo before I can decide.