The specs look just the same for the MaxBotix LV MaxSonar EZ series sensors and they all look alike too. You may experience déjà vu when reading the specs.
The big difference is the shape and detection abilities of the ultrasonic beam. Here's a chart...
The EZ0 has the widest beam width and is well suited to detecting obstacles such as people or small objects for collision avoidance but the wide beam means you cant tell with much precision where the object is, only that it is there.
The EZ4 has the narrowest and least sensitive beam so it is better suited to more accurate detection of features such as the location of a door to navigate through or the location of other objects for mapping.
The EZ1, EZ2 and EZ3 fall between these extremes and offer a good compromise of features for either object detection or location.
Since they all look the same there is a coloured dot on the back of each sensor so you can tell them apart.