2 Stem swivel casters on one end and 2 Rigid casters on the other end is probably the most widely used. An example of this is a baggage cart at an airport. You should push from the swivel end and the rigid casters allow you to maintain a straight line when pushing the cart long distances. The disadvantage is that you have to “park” it to get it against a wall as you can not push it sideways.
4 Stem swivel casters is another widely used arrangement when you need to maneuver in confined spaces. This is typically seen on a “furniture dolly”. The advantage to this is that you can push it sideways, spin in place and make tight turns. The disadvantage is that it is difficult to move in a straight line when pushing heavy loads long distances.