I think the one question I get more than anything when I'm at work is "Is there even a difference between the Urban Decay Naked Palette, and the Naked 2 Palette?" YES. Yes there is. And many makeup junkies will tell you the same thing. Yes, there's a difference. Do you need both of them? Probably not.
The one similarity between Naked and Naked 2 is that they both contain the shadow "Half Baked" which is a light gold color. That is the only shade that is the same. They also both come with a brush. Naked Palette comes with a shadow brush. Naked 2 comes with a double ended brush... one side is a shadow brush, and the other side is a crease brush. The important thing to know about the Urban Decay brushes (and this goes for all brushes made by Urban Decay) is that they are made out of recycled synthetic materials... and because of that, you want to clean them with rubbing alcohol. That's it. Just rubbing alcohol.
Now, I could go into depth comparing each shadow in both palettes, but I'm not going to do that. The main difference between Naked and Naked 2 is the tone. The Naked Palette has mostly gold and bronze colors, whereas Naked 2 has a lot of taupe, grey, and "greige" colors (grey/beige). Basically, my suggestion is if you are a warm-tone, get Naked. If you are a neutral tone, get either. If you are a cool tone, get Naked 2.
If you have no idea what tone you are... look at the color of clothing you wear. If you look great in orange, red, gold... if you wear a lot of yellow gold jewelry... and if you wear a lot of "earthy tones" for your makeup (browns, greens, peaches) then you would like the Naked Palette better. But if those types of colors don't match well with your skin tone, then think about Naked 2.
Personally for me, I prefer Naked 2. I do have them both, but I wear my Naked 2 more than Naked. People who are Urban Decay Addicts will get both. You don't need both... not really.