So assuming all else is equal, if GovBook has a charter to harness data only for the public good (and Facebook certainly does not) then GovBook wins.
But we don't know the specifics how much easy it is / how much they access / etc., w/r/t NSA & GCHQ access to data from Facebook, Google, Twitter, etc. But with a State run site, I think we can safely assume they will have access to everything, no questions asked.
That said, this seems like more of 1a / 1b thing, and neither option is exactly appealing. For those of us in the public at large, the real answer is probably some variation of "the only way to win, is to not play".
So assuming all else is equal, if GovBook has a charter to harness data only for the public good (and Facebook certainly does not) then GovBook wins.
I don't trust any State government to do anything "only for the public good" and I can't imagine how anybody could think such a thing. Our governments are tools of the rich and powerful and exist to protect their interests. Any "public good" is an incidental side effect at best.