MacBook Pro :: Difference In Battery Time 45 And 60 Watts

I'm in to buy a second hand Macbook unibody - the one that didn't exist for very long, until it was slightly upgraded and rebranded as Macbook Pro. 13,3".

Differences I've found so far add up to these:
45 watt changeable vs 60 watt built-in battery
2.0 Mhz vs 2.26 Mhz
- vs Firewire 800 and SD card slot

One question would be - how much does the battery time differ between 45 and 60 watt?

Then I heard that the screen might have been updated too, something that for me makes more value than all the above. A quote comparing the white Macbook ("WhiteBook") with the unibody Macbook pro: "While both machines have 13.3-inch glossy displays, the unibody has also been upgraded to a higher-quality screen from AU Optronics with 60 percent greater color gamut, another advantage over the WhiteBook."

Does the unibody Macbook have the same screen as the white macbook, or does it have the same as the unibody Macbook pro - or something in-between? Does someone know of a comparison between the two?

I'll do a lot of graphics - picture editing - so it's important for me.