I have a DSlite and I've been very pleased with it while I was using it (got bored of it about a year ago)
It's still a great buy probably considering the portability of that little thing, but I'd strongly compare it to a PSP in terms of 3D graphics performance.
truth be told I think DS should have stuck to 2D graphics until they bumped the hardware to significantly higher level. In todays day and age having PSX 3d level graphics is just, well sad. I've seen enough of FF7 triangles back in the day, I don't know why they choose to keep doing it while producing modern titles. (meh, I'm probably rambling now, but that's just IMHO)