I think there might be seniors who can answer but in my point of view the difference between the PSP and fsp is that PSP have the power, athority, and social respect they the vehicle and house but in big cities you have to arrange the house with your own self but in fsp they have to go to foreign countries and fully furnitured appartment and while you are in foreign country they will pay you high and the two sons/daughter their college/school expensives are on govt so I myself love fsp rather than PSP. PSP is also the top three priority of the candidates but depends upon you that what you wanna select what do you like more power, athority/ forieng tours, and spend luxurious life and at last they of both fsp and PSP in Pakistan is same but in forieng countries the fsp is leading in salary.
Wish you a best of luck and don't me in your precious prayers...