Swivel wheels make turning the object the wheels support easier, but they can also make it difficult to control. Pushing a cart or other item with swivel wheels in a straight line, particular on an uneven surface, can be difficult.
Swivel wheels make turning simple; light pressure can turn even heavy items, and turning in tight spaces is easy. When pushing a cart or stroller with fixed wheels, the person pushing might need to apply a significant amount of downward pressure to get the wheel to turn. Fixed wheels often have larger turning radii as well, so turning in tight spaces might require lifting the cart to reposition it. Another advantage of fixed wheels is their versatility. Sand, grass and other surfaces can make it difficult to push a cart with swivel wheels, as they tend to turn frequently and get stuck. Fixed wheels are better able to handle these conditions.
Pulling instead of pushing a cart can mitigate some of the disadvantages of swivel wheels, as the wheels can't misdirect and send the cart off track. It's possible to use both swivel wheels and fixed wheels to take advantage of both types. Placing a fixed wheel at the front can provide stability and keep the cart on track, while swivel wheels at the back can make the cart easier to turn.