If it's assume that increased resolution = smaller visuals perhaps.
This isn't the case with Windows for example, the quantity and size of items (icons, fonts, etc.) displayed on the screen isn't necessarily linear with resolution, but the higher resolutions will display the same icons/pics/vids/texts with better clarity so they appear clearer and less blurred/aliased, which can mean not having to stick your nose right up to it to make things out.
Same route the iphone4 went with an oversized resolution, but with a smaller screen footprint than the Streak so it isn't as high as this proposition. I bet the content on the iphone4 isn't providing a big difference in real estate compared to iphone3, but it should be clearer to use and easier to read the same things on it (in theory).