[H]Enthusiast has done a Lost planet reviews which casts some more light on DX9 vs. DX10, ..interesting read!..
excerpts:
"The fact that DirectX 10 is causing all the video cards in this evaluation to lose performance, when no major image quality enhancements are being made, is quite disappointing. DirectX 10, along with the ability to allow better shader effects, is supposed to be more efficient than DirectX 9. You would think DX10 performance would be slightly faster, but all the video cards tested here were slower in DX10 mode at the exact same settings, some more than others."
"There isn’t a major image quality difference between DX9 and DX10 modes. There are some contrast differences, and some texture differences outdoors, but otherwise everything is the same. The one major advantage this game does have is the “High” shadow option in DX10, but no video card currently is able to render it fast enough unless you sacrifice other image quality options."
http://enthusiast.hardocp.com/article.html?art=MTM3MSw2LCxoZW50aHVzaWFzdA==
excerpts:
"The fact that DirectX 10 is causing all the video cards in this evaluation to lose performance, when no major image quality enhancements are being made, is quite disappointing. DirectX 10, along with the ability to allow better shader effects, is supposed to be more efficient than DirectX 9. You would think DX10 performance would be slightly faster, but all the video cards tested here were slower in DX10 mode at the exact same settings, some more than others."
"There isn’t a major image quality difference between DX9 and DX10 modes. There are some contrast differences, and some texture differences outdoors, but otherwise everything is the same. The one major advantage this game does have is the “High” shadow option in DX10, but no video card currently is able to render it fast enough unless you sacrifice other image quality options."
http://enthusiast.hardocp.com/article.html?art=MTM3MSw2LCxoZW50aHVzaWFzdA==