Hydrostatic is the most accurate, but it still includes fat stored inside the body in the final figure.
9 point caliper is the best for most of us, since we don't have immediate (free) access to the hydrostatic testing.
I don't have the 9 point info, but I use 7 point with a computer program. I also feel that the mirror is the most important way to to monitor your bf. The reason being that bf% is only a number. Don't get too hung up on it. 99% of the guys that talk about being 10% bf are actually a hell of a lot closer to 20% in reality. Seeing your abs???? It is likely that you are 20 or slightly higher, but that really isn't what any of us like to hear. So worry more about the direction of the numbers you are seeing with your calipers than anything else. Also pay attention to the mirror. Because for 99% of us, that's the ultimate goal anyway.