Hire a property management company or hire an FTE?

[Willie Mandrell]

I currently have  25 rental properties (spread among mostly 3-family properties in the greater Boston area).  Over the next year I want to double that portfolio.  Before I do that though, I want to ensure that I have a solid system in place to manage the rentals that will be able to scale with me.  Up to this point I've managed the properties, but going forward I'm considering a couple of different options:  invest in a property management software program (Buildium, AppFolio, etc) and hire a part/full-time person to focus solely on that OR source the work to an existing property management company.  Thoughts on the strategy or approach.. or any other options?