The only difference is in what's been selected in the model type when the
diagram was first started.

In ERWin 7.3 you have the choice of creating three different kinds of
diagrams:

1) Physical

2) Logical;

3) Physical/Logical.

In order to have a Logical diagram with entities which automatically transfer
to the physical diagram then you must start with a Model that is of the type
Physical/Logical.

After you create entities in the Logical model you then click the down arrow
on the top middle of the ERWin GUI to select Physical and ERWin changes to the
physical model and the logical entities you created in the local model are
automatically in the physical model - unless you tagged the logical model
entities to only be in the logical model.

Another difference may be that in the logical model a many-to-many
relationship may not contain the node table but in the physical model the
many-to-many relationship should contain the node table.