Property management is a such a critical part of the real estate investing equation that it could very well mean the difference between a profitable (or positive cash flow) situation on a well leveraged property and significant negative cash flow.
So, with a decision that is that important, the question is: do you leave it to the professionals or do you only trust yourself to do the best job? Well, having done property management myself and hired professional property managers to do it for me, I can tell you that there is no easy answer.
In fact, if you pick the wrong property manager you may wish you did it yourself.
The challenge is that you may be the wrong property manager.
A property manager needs to be able to follow a proven, written set of systems and checklists.
If you're not that type, I would suggest that you find some property management company that has good, well documented, proven systems for managing your properties and leave it to the experts.
Of course, if you've got access to some great written systems, like dealing with tenants during the previewing, application, screening, move in, tenancy and move out processes than property management might just be something for you.
I would encourage you to interview a few property managers--using the same interview questions for each--and then answer the same interview questions yourself and see which person you'd like managing your properties.
If you find that you wouldn't hire yourself as property manager then I would strongly suggest that you hire out the expertise that a professional property manager brings.