There are 2 differences:
2 methods creating a user and granting some privileges to him
create user userName identified by password;
grant connect to userName;
and
grant connect to userName identified by password;
do exactly the same. It creates a user and grants him the connect role.
different outcome
resource is a role in oracle, which gives you the right to create objects (tables, procedures, some more but no views!). ALL PRIVILEGES grants a lot more of system privileges.
To grant a user all privileges run you first snippet or
grant all privileges to userName identified by password;