Unless you have the brightness on really high
One thing, there is a bug (the DSi has it too), then the backlight is turned off (Super Mario 64 DS can do this), it is difficult to see past the thick screens. This is the only real reason I can see for getting a DS lite over the Plat, aulthough, the Plat. is only slightly brighter (One can barely see this) than the DSlite when it is on it's lowest brightness setting.
I still recomend a DSi, because at any time, one can hold SELECT, and press the volume buttons to change the brightness. AT ANY TIME!!!
Here I am, testing this to be true (that tells that I really do not support the DS lite). Lengthwise, it is about 3/4 inch shorter, Widthwise, it is less than 1/2 inch shorter, Heightwise, it less than 1/4 inch shorter. Also, the power switch is on the outside, so if you put it in the pocket, it may turn off. (That is an improvement of the DSi, putting the power switch on the inside).
That is an opinion, not a fact.
I honestly have no preference on this, and it is no reason to turn down the Plat.
Take the screens, for example. The Plat. has a much stronger transparent layer for the top screen. On the lite, one can just barely tough it, and it will have the colory things displayed, which it really bad.
For the Plat, one has to mean it, and I don't want to exert pressure for it to even slightly appear, because it requires that much pressure. As for the touch screen, I wouldn't be supprised if the Plat's touch screen was made of plexi-glass.
The buttons are cheaper, too (thank the LORD that nintendo made them better quality with less plastic). The DS lite's buttons wiggle around all over the place due to insufficient planning. The Plat's buttons are amazing quality. I still recomend a DSi, because unlike the DS lite, Nintendo really spent time planning it.