As far as coyotes go you will call more numbers at night but your kill ratio may not be as good as calling in the daytime. For most folks calling Bobcats maybe the opposite as they can pick up the eyes and see them at night. Most Bobcats called in the daytime are never seen by your average caller.
I personally "enjoy" calling in the daytime more and that is my preference but some area's are more conducive to night calling due to various reasons.
"Anyone taking up handloading necessarily plays with unknown factors and takes chances. But so does anyone who drives a car,goes to a cocktail party,eats in a restaurant,or gets married."
Jack O'Connor 1963