Let's split it between: video quality, features, and media/size.
Video quality: Is close between the two. From what I have seen, the SR10 seems to have an edge. This site
http://www.camcorder-test.com/camcorder.html agrees; the SR10 scores 333, the HC9 scores 298.
Features: The SD9 has the option of a progressive mode, the SR10 does not. The SR10 can shoot in SD or HD, the SD9 only in HD. Apart from that they are similar in features.
Media/Size: Sony, with the HDD, is larger/heavier than the SD9. With HDD you can shoot for a long time with no changing media. But if the HDD fills up you are stuck until you can empty it. With SD9, you can buy as many SDHC cards as you need.