easy...check ur monitor resolution when u're in game...i tried with samsung 2233sw...i set it to 1080p(d monitor supports it for sure) in the XMB screen
there is a menu screen that displays the resolution and frequency, now is 1920x1080

when i start the game(i.e. naruto or other 720p games, it'll auto switch b to 720p) the image seem softer
then i put in a 1080p game(i.e. GT5p), i'll get 1080p which image is sharper

the sony thingy mentioned, i guess its kinda marketing gimmick to me...
they stated 1080p compatible, its jz that simply means it "ACCEPTS" 1080p signal den downscale it to 720p/1080i
the panel itself's resolution i believe its only HD ready, 1366x768

there is no nid to debate 720p or 1080i which is better, trust ur own eye..which setting u prefer, den stick to it