Well as for hardware power goes there about the same both have 600mhz arm cortex a8, I think they both have 400mhz 3d accelerator, and they both have 256mb of ram. However the Sony Ericsson Satio would because of 12mp camera with xenon flash vs 5mp camera with dual led flash and records video at better quality and framerate. The Nokia n900 would win because of 32gb of internal memory vs something like 256mb with 8gb microsd card also n900 has a physical keyboard which is a nice touch look a little cramped for my taste but better than onscreen qwerty. Mostly hardware is equal n900 wins because of more storage and Satio wins because of a better camera. Also n900 has 768mb swap file.
I would say the Nokia n8 looks very nice but I don't like how it uses a capacitive touchscreen because I like to use a stylus. Also I would say the n8 a has edge over the Satio I will wait to see if Nokia doesn't release another disaster like the Nokia n97.