Can somone give me info on the different PSVita models?

There are two models, the 1000 and the 'lite', 2000. There are different colour variants, but they're almost all for Japan, but they are not new models.
The 1000 has an OLED screen which is superior to the LCD on the 2000. The OLED has much richer dark colours as it's capable of showing 'true' black - while the LCD has a backlight so even black has a degree of illumination. If you've used an OLED version then you'll probably dislike the LCD, but the LCD one is by no means a 'bad' screen by itself.
As well as the screen difference, the 2000 model has a better battery life. You might struggle to even find a 1000 these days so I'd say just go with the 2000.

There is also the 1100 model, which I own. Not visible difference with 1000. Guess it's internal circuitry upgrade. But yes - the 1000 models have superior screen and only black case color. The 2000 models which are called Vita Slim, have slimmer case, multiple case colors, not so good screen but 1 hour more battery life. There was also the 1000 3G model which you can use with a SIM card to have on-board internet, but this model is long ago discontinued. Any 1000 model is now discontinued. I guess you can still find some on eBay. The screen on my 1100 is what made me buy it. I disliked the screen on the 3ds. However now better go with the Vita Slim (2000) - more battery life, slimmer, colorful case.