The Slim feels way nicer to hold in my opinion. I also love it's battery life too and the fact that it uses a micro-usb cable. I bought a 1000 and 2000 model last month from Amazon to decide which I wanted to keep. Sure the 1000 feels like it's built a little more secure but it's way more heavy/bulky and unless you get one brand new, the joysticks often feel pretty loose. I ended up sticking with the 2000, however I ultimately returned it to get a brand-new blue slim so I could put Henkaku on it. OLED also consumes more battery so I'm perfectly happy with the LCD screen. I also have agree with WiiUBricker, the 2000 model was brighter. After doing a comparison, it's clear (atleast to me) why Sony upgraded the Vita to a slim model. It's sleeker, comes in cool colors, has an insane amount of battery, and uses a micro-usb cable.
Also, did I mention that it feels way nicer to hold? lol