What are the similarities and differences between eubacteria and archaebacteria?

The differences are that archaebacteria are found under extreme conditions like volcanic vents, while eubacteria are found in neutral conditions like the human body or foods. Archaebacteria are single-celled while the eubacteria are more complex in nature.

The first similarity is that they're both bacteria. They both also look very similar under a microscope. You don't notice the difference until you look at them at a sub-cellular level.