I drew up a little chart
comparing the 3DS specs to the PSP and iPhone 3GS (thanks for finding the slide, Karas!).
It's hard to draw a conclusion right now, since the specs they list are for 100 MHz clock speed. They say that it draws up to 1 mW per 1 MHz clock speed, so at 400 MHz, it is only drawing 400 mW.
I quickly tested my PSP-1000 to see how much power it draws in a top 3D game (MGS Peace Walker should suffice) and it it drawing up to 2100 mW during a 3D scene with the lowest screen brightness. Sitting in the main menu, it draws 1500 mW, so that tells us that the combination of 3D and audio is drawing 600 mW. It isn't unreasonable to assume most of that is going to 3D (certainly up to 400 mW) which puts it right in line with a 400 Mhz Pico 200 chip in the 3DS.
It's hard to draw a conclusion from 100 Mhz specs though, since fill rate may not scale directly with clock speed (vertex rate should though, I think)