It's because the card and the matches in display "whatever". Also, you are making a DX10 game work more to change things to DX9, that would also affect FPS. So your thoughts are correct.
thats odd a lot of prior observations are that DX10 really lags the game up like with company of heroes...but maybe cause thats cause it wasnt really a TRUE DX9 game...anyways Bioshock definately has a lot of graphical problems right now that gamespot cant explain.
From DX10 vs. DX9 screenshots of Bioshock, there wasn't a significant difference.
pinoy, man....make your sig smaller....it's too freakin' big...and you don't have to tell the community, that it's "Pinoy's Build". We know that already.