Practically and ergonomically I prefer a centered lens. Your hand has to reach less far to reach the focus ring and aperture control. Most slr cameras have buttons on both sides of the lens, so developing muscle memory is easier when those actions are split between each hand. Rotation of the camera is also much more natural. It also centers the lens' pov between your eyes, matching their parallax, which is really important for composing the photograph outside of the viewfinder.