Wow. I had no idea. The LTD DS numbers are so much greater than the LTD GBA numbers (153.93M vs. 81.51M) but I didn't know that its launch was comparatively so much slower.
Actually, in North America, the final numbers were a lot closer than the Worldwide totals would leave you to believe:
Gameboy Advance Shipments to NA: 41.6M
NDS Shipments to NA: 59.9M
The DS still "won" by quite a bit, but it was only a 44% increase over the GBA, compared to the 89% increase worldwide. NDS almost doubled the GBA in Japan, and almost tripled the GBA in PAL countries.