In a condo you have communal property you all have to maintain (the elevator, the roof etc, if they break you're all screwed).
HOAs usually don't have that (maybe some roads that should be adopted by the local government...). Instead their rules are specifically about lifestyle and appearances.
Sorry I wasn't very clear. In a condo, you have shared assets like a roof and stairs and a front door and elevators. If they fail is a huge problem for everyone. In an HoA, you don't really share any VITAL components. You might all contribute to the upkeep of a park or a pool. But if the park or the pool are neglected, you can still live in you're home. You're actual home is self contained and yours alone.
HOAs usually don't have that (maybe some roads that should be adopted by the local government...). Instead their rules are specifically about lifestyle and appearances.