I don't know I had a GBA(not SP) with an afterburner light and it looked really washed out.
When I got my first DS(phat) I realized that the new SP SE had a far better screen, and I lost my sleep over that untill I decided to get one.
The GBA SP SE screen is so much better than the original DS, that for a while I went back to GBA gaming only.
Then I got a DSL, and I agree that the screens are a little bit sharper and the colours look somehow cleaner then on the GBA SP SE, but when playing in GBA mode I have those black bars around the screen and the image looks slightly smaller than on the SP, therefore I still use the SP for every GBA game(and also GB and GBcolor) and the DSL only for DS games.
I often think of the GBA SP SE as the defenitive gameboy machine, backwards compatible with every game,and I will use it forever when it comes to gameboy games.