PRO: When living in a Condo or Townhome, you have more opportunities to say "Hello" to your neighbors, and to get to know them. Because you share common areas with them, most likely, you will see them more than if you both lived in a housing subdivision. You might find that this leads to a greater Sense of Community.
CON: You might not like being so close to your neighbors. For example, what if they play their music too loud next door? No one likes to be a "party pooper", including you! If you do not feel on good terms with them, you might prefer to avoid them, but this may be hard to do when traversing the common areas.