To answer your question:
The PSP has a CPU underclock at 222 MHz on pre-install firmware, but now runs at 333 MHz if you got the Firmware updates.
The 3DS has its 2-core CPU clock at 800 MHz a core on pre-install firmware 1.0.0-0, and might be currently clocked at more then 1 GHz a core on the current firmware of 5.1.0-11.
The PSP is weaker then the PS2 which is weaker then the GameCube, which had a GPU of 194 MHz, so it's a safe bet that the PSP GPU is less then 190 MHz, while the 3DS has its GPU underclock at 400 MHz (PICA200, 2010 model, there's also a 2008 & 2006 model. The 2006 model can do 400 MHz max clock). Anyways the 3DS on pre-install firmware can only handle GPU at 400 MHz. (the Wii U on pre-install firmware can handle GPU as high as at 800 MHz)
The 3DS pixel performence is 1.6 billion, and has around 60 shader cores.
The 3DS 2D resolution is 800 x 240 vs. the PSP 2D resolution of 480 x 272.
If the PSP could do 3D, then here's what the 3D resolution comparison would be for side-by-side 3D:
3DS = 400 x 240
PSP = 240 x 272
