Just ask the Experts at Digital Foundry OK?
http://www.eurogamer.net/articles/digitalfoundry-vs-nintendo-3ds?page=1
"What we do have is a massively significant increase in rendering power over the existing DS, leap-frogging the PSP and probably offering around the same horsepower as a Dreamcast, maybe in some respects giving PS2-level performance. But from everything I've seen so far there's no sign of the sort of rendering features that you see in iPad or iPhone 3GS, so no evidence of programmable pixel shaders or other state-of-the-art OpenGL ES 2.0 loveliness."
"That being the case, to compare 3DS with Wii, or even GameCube, in terms of graphical quality based on this beautiful demo probably doesn't do the home console justice. The best demos we see based on actual game assets are of Dreamcast quality."
My opinion is, PSP already lost the battle to the DS even it has much more graphical power (PS2 vs N64, which is night and day), it can still barely hold on in Japan because of Monster Hunter only, a third party game which can jump ship any minute.
The difference now between 3DS and Tegra 2 is only between shader and no shader, to be flank, I wont know the difference. The only thing Tegra 2 might offer is ease of development by utilizing Open Gl on familiar Nvidia architecture by most of developers.
PSP2 need to have groundbreaking technologies to counter the naked eye 3D effect of 3DS, polygon numbers doesnt matter now. Dual analog for FPS and no-stylus Capacity touchscreen for adventure game is a must.