Re: 04-05 vs 06-07
I don't know why everyone says they are so wheelie prone. My 06 seems to hold the nose down pretty good though I do stay on top of the tank as much as possible. I have seen it come up more when I'm not as focused on leaning forward. The way I sit on it seems to make a huge difference. It might be because I'm a smaller guy too. A buddy of mine was messing with me on his 06 GSX-R1000 and his tire kept popping up and making him have to slow down. He's a pretty big guy so that's what made me think it has a lot to do with your size/position.
As far as comparison for the years, I've only had this 06 and only heard they are a tad faster/more reliabile.