[FastRX8]

Higher DPI just makes it smoother.
In Windows mobile you have the option to change your font size, so that will affectively show more lines of text,
but because the overall screen size is the same, the font maybe too small to read.
It would be like doubling the DPI on your pc's display.
Compare your pc at 800x600 vs 1600x1200.
However, w/ the Diamond, you have the scroll wheel, which allows you to zoom in/out in certain windows, like emails, to change the font size.
The higher DPI just makes for a better looking display, and it gives you the option to shrink your font size w/o losing cleartype quality.
If you're eyes can handle the smaller font, you can definitely fit more text on the screen.

BTW - I expect your post will be moved to another forum, as this forum is now for posting custom roms only.