My rule is what counts and the first criteria is to have the bar at the right location. Second is to have the cables as short as possible with the maximum radius and minimum bends. As stated, the stem will dictate if the cables run in front or behind the bar. I am one of the few with the front brake controlled by the right lever. The result often is that the cable don't cross. WRT the rear cable rounting around the stem, it is determined by how much the cable is "stretched" when turning the wheel.

In addition is the issue of the rear brake cable housing from either the clamp or exit of the tube to the brake. My preference is not to have it bend up to go down. The criteria for me is to avoid the cable rubbing on the frame. If the rule for the front is followed on the back then it will rub on the frame, depending on the exit location of the clamp/tube exit.

Having been so straight forward in the above comments, I don't really care too much how other do it. To me it is all about cable/housing performance with economy of cable/housing length, in that order.