DS just is a wonderful console. I never thought I would enjoy portable gaming very much but I´ve changed my mind since I´ve gotten the DS. The only thing I really miss right now is a new 2d Metroid. I also think that DS would be the perfect platform for a new 2d Kid Icarus! Just think about it, a new game in the same style as the old NES game but with much better graphics and way more courses! Of course I´m just dreaming here.

DS by far.

Reason? Layton and Nintendogs.

It has Okamiden. Enough said.

Actually, I want to change what I said before.  I can make a definite choice which system is better right now.  While GBA may have had Metroid and Castlevania, pretty much the DS is on top basically because of all the RPG and 2D platforming attention its getting. Even the GBA didn't get as much attention as the DS has in these areas. Especially how the DS has gotten 5 major Dragon Quest titles (and three others) or a ton of platforming games (Metal Slug 7, Contra 4, New Super Mario Bros, Three Kirby titles, etc).

DS is WAY better than GBA. I can think of individual DS games that have potentially gotten more playtime than my entire GBA library.

My vote for the DS. There is no RPG on the GBA that i love more than The World Ends With You, which says quite a bit when ive gone through both my golden suns at least twice over.

Also - variety. EBA + yu-gi-oh + mario kart + club house games + current RPG in my pocket makes me a happy DS owner...and the fact that the above games all fit in my wallet is a big plus.

Far superior

DS, no contest, better and more rpgs, online shooters , more castlevanias with more features....and
scribblenauts..that alone destroys any gba game in innovation

GBA had a lot of remakes and "pocket" versions of console games

but DS has (localized) Phoenix Wright, so it beats every console and handheld ever made. yeah, I said it.

DS has a much more quality library than the GBA, which IMO had a pretty impressive library.