What in the world?! You should have tried them out this past weekend! My sister and I both brought the PSP and 3DS to kill time in line... HA HA! But yeah...
The 3DS can switch back and forth between 3D mode and Standard mode, so it's the flick of a switch if your eyes start to hurt...
Graphics... GRAPHICS ARE FUGGIN AWESOME!!! I don't know how far it can go or how great the hardware is, but it was running Resident Evil 5 graphics on it pretty smoothly, and keep in mind that RE5 was made for the 360 and PS3...
The 3D part is amazing! Like the hardware though, I don't know if the current models will have any bugs, but it REALLY DOES 3D!!!
The unit itself is a bit bigger, which is good for me since the original DS was too small for my hands, but the best feature is the addition of an analog pad (FINALLY!)... It's concaved instead of convexed, so it grooves easily into your thumb...
The PSP is just what it was as the previous models... Strong, reliable, and never lets you down... What you should be waiting for is the NGP, Next Generation Portable, that's replacing the PSP...
The only major difference in that is a second analog for the right thumb, so it's just like using a dualshock controller...
Graphics and all that other jazz, I shouldn't have to mention...
It depends on what you want to use your system for... I haven't fiddled around with the 3DS much yet to see what it's really capable of, but I think both of the units is a buy... Although I'd say wait for a price drop on the 3DS unless if you REALLY need one...