the one big advantage the hv30/40 has over the hf10/0 is the viewfinder. im not sure how well the lcd is on canons in bright light, but it can be a hinderance. i also find it easier to steady the cam when pressing it against my face. also the hf only has a 2.7" lcd, with a lower pixel count

i think the only real difference you would see in image quality between the 2 would be any fast motion may cause some trouble for the avchd cams

i personally want to get into using flash memory for cams, but i hate the lack of viewfinders and i hate working with the avchd format since i dont want to buy a specialized editor