At the moment it's the DS. After hours of looking at online videos of games for both consoles my mind is now made up (well at least for today). I will buy the DS when it comes out in England. The price cost and the fact that Nintendo really know what they're doing in the handheld console market has swung my vote. The PSP looks fantastic, but so did the N-Gage at first and till I'm sure that the console will be a success, I'm not buying it! 
James 