Well, I know I'm a more unique situation, so my preference is whenever, lol. But I'm sure for most hobbyists, it's easier to explain time differences during the week, especially when dealing with a significant other, than on the weekend. And just plain easier to be out of the house/apartment during that time as well.
You can normally spot us guys without a SO as we are the ones who want late nite or weekends, for me it is both as I have to travel just to enjoy the beautiful ladies of KC and My boss is a jerk ( did I say that I work for myself). my 2 cents.