The N900 has a Transreflective TFT LCD. It performs insanely better under sunlight. Transmissive displays (like the one in the N97 Mini) gets whooped under sunlight. Severely whooped. They're totally unusable under direct sunlight, whereas everything is still visible on the N900, just quite monochromatic in appearance.

EVERY LCD (used in a phone) has a backlight. [OLEDs are not LCD's, before anyone suggests it. And (for example) LCDs in watches don't have a backlight, in case anyone wonders.] Ask him to GoogleTFU first, before acting like an expert. The N900 has a Content Adaptive Backlight Control (Backlight adjusts according to content on screen, finally found the goddamned name) + Light sensor. There is no such thing as a light sensing screen on a mobile. The small hidden circle near the top left edge of the N900 (usually very hard to see) is a light sensor. It alters backlight's brightness automatically and subtly. To adjust, go to Settings > Display. The adjusting is allowed by a check next to power saving mode.

The N900's display doesn't have the best contrast, which will make it look duller, but IMO the colours are more accurate, since I find the BB Bold display oversaturated. The N900 is also limited to 65k colours, but that's quite unvisible unless you view an image with a gradient.