The two approaches are completely different in the amount of beans created.
When the bean has a
scope="prototype"
this means a new bean instance will be created everytime you ask for a bean with the correspondingid
.When the bean doesn't have a
scope
attribute set, this means a single instance will be created when the context is loaded for the first time and will be shared.
I believe the time consumed for creation of prototype and singleton beans is (if not the same) very close.