The machines are basically identical in all ways except for screen size. The dv4000 is a 15.4" screen while the dv1000 is a 14" screen. The dv1000 has a little go button next to the arrow keys for manual navigation, but otherwise the buttons and everything are the same. The price is the same between the two when you compare apples to apples. The size and weight are different, obviously, and the dv1000 does get slightly better battery life. Both have an optional remote control. I personally think the dv1000 looks cooler - has shiny black around the keyboard and more blue leds.
The dv4000 does not currently have a Radeon X700. If you need the laptop now, that won't be a factor. If you can wait, the X700 would be a much better card, but we'll have to see how this affects price. Currently, both have the intel gma 900 onboard graphics processor.
The deciding factor for you should be whether you want a smaller 14" screen or a larger 15.4" screen. Note that the resolution of both are exactly the same (WXGA), it's just that the 15.4" will have everything bigger. In other words, you won't be able to fit more on the larger screen, but what is on the screen will be larger than it would on the 14" screen.
(Personally, I like the smaller, lighter laptop, but that's just me).