There are pros and cons to Professional Management as well as pros and cons of Self Managed.
There are significant advantages to professional management with the trade-off being cost. Professional management costs money.
No headaches with dealing with the property
Easy to have things done, one stop shop
They have professional contractors on hand
Ability to perform a reserve study easily
History of managing other properties
It costs some money for professional management
Sometimes slower to evaluate new contractors
Depending on the association, they can be slower to respond to requests
Sometimes you don't get to know staff since they usually are not on-site.
The main reason for self-managed associations is that it generally costs less. If you have a small association, this is usually fine as there isn't as much work to do anyway. On larger association properties, there is much more to managing the association that being self-managed usually doesn't work.
Having the ability to move very quickly
Having more control over evaluation of sub-contractors
Knowing the people that managing the property
Keeping costs down.
Getting overloaded with paper work or busy work related to the property
Not having people volunteer to run portions of the association
Keeping track of funds (accounting)
Dealing with non-payments
Dealing with law enforcement
Having to evaluate sub-contractors
Having to do repairs on the property
Relying on others in on the board that don't know anything about maintaining a property
Having to issue HOA paperwork for purchase agreements
One big difference
Professionally managed associations will have professionals making suggestions as to how to run the association. It is still up to the board and the association members as to how things happen but having these professional suggestions helps immensely. The biggest issue I have seen is reserve funds. Many times in self managed associations, the members of the association (the owners in the complex) will always vote to not increase dues, and to not build up the reserve funds. This is often because they don't know the implications of not building up reserve funds, and how that may impact the financing of maintenance and upkeep, such as a roof replacement. Oftentimes they will assume that they can just assess each unit owner and have special assessments on each unit. That may or may not be the best idea. Sometimes it may be difficult to get financing, or sometimes it may require bonding, which may or may not be able to be paid off at closing. If the assessment cannot be paid off at closing, then the sale price will be affected.