Hi, so a little background info first. I just purchased a 7D and need to buy a compact flash card, looking at getting one larger card first and then eventually getting another backup later. I will be shooting action, football games, baseball, track and field, and some bird watching. I'm debating between the 16GB 600x and the 32GB 400X. I know this question has been asked a lot and I have read the posts. Unfortunately since I dont have the camera yet I'm wondering if the difference in speed will make a significant difference for what I'm shooting.