Rahul Kumbhar
Ansys Employee

In Share topology, the common faces betweent wo bodies are merged into one. The bodies are separate but its face is shared. So when you generate the emsh, the nodes on the common face are shared between elements on two bodies.

The bonded contact, a contact is defined on two surafces of these two bodies. The nodes are not common. Additionally there are contact elements on both faces. Ideally you should get similar result using Shared topology and bonded contact.

Merrging bodies does not keep any common interface and thus it is continuous single volume with same material properties.