Honestly, I would ask your colleagues what they would do. If you plan on staying in that field, they are the ones who you should be asking for advice. Also, what do you want to study!? SSP curriculum is geared toward those who are in the DoD, while GSPIA courses seem to examine these issues from a variety of perspectives.
While SSP is one of the most repsected programs for those within your line of work, if you already have a career you like locked down, will a degree from SSP give you that much of an advantage over one from Pitt? IMO if you plan on staying in the public sector, go to whichever school you would enjoy more.