Dbu (dialog base units) have one purpose, and that is to scale with system setting font size; Once known as "Large Fonts", now called "Set custom text size (DPI)" (dots per inch) in Vista/7/8. Also known as Ppi for Pixels per inch.
ANYWAY, if you want things to scale well for those weirdos who adjust this setting, go ahead and stick with DBU, and test your creation with various system font magnifications.
