I've only done overnight camp and I've loved every minute of it. I have done 8-week camp and 1-week camp. I like both for different reasons. The 8-week camp was nice because you really got to know your campers and all of the campers at camp really well. The 1-week camp is nice because you get to help lots of different kids grow and learn. You also can repeat things more than once without having to worry that the campers won't like doing it since you get new campers every week.
I can say without a doubt that I'm an overnight camp person. I don't think I could do day camp at all.