I have to assume the natural question is then "which end?" If you put them at the top and the left of vertical and horizontal bars, they're inconveniently far apart when you want to pan different dimensions. If you put them bottom and right, it's very easy to move the window so they're off the screen entirely. But then that's a problem you have with split controls anyway. It feels like there is no good choice here, and split is on average least bad.